Method for transmitting and receiving data in wireless communication system, and device therefor

ABSTRACT

The present invention relates to a method and device for operating a terminal in a wireless communication system. According to the present invention, downlink control information is transmitted to a terminal and can include symbol information related to the last symbol of a downlink shared channel. A method and device can be provided wherein a terminal transmits a first demodulation reference signal (DMSR) and at least one second DMRS for demodulating downlink data, and transmits data through the downlink shared channel, and a symbol position to which the at least one second DMRS is mapped is determined according to the symbol information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 17/108,580, filed on Dec. 1, 2020, which is a continuation of U.S.application Ser. No. 16/824,990, filed on Mar. 20, 2020, which is acontinuation of International Application No. PCT/KR2018/013823, filedon Nov. 13, 2018, which claims the benefit of U.S. ProvisionalApplication No. 62/585,457, filed on Nov. 13, 2017, and No. 62/586,214,filed on Nov. 15, 2017, the contents of which are all herebyincorporated by reference herein in their entirety.

TECHNICAL FIELD

The present disclosure relates to a wireless communication system, andmore particularly, to a method and device for generating andtransmitting a demodulation reference signal (DMRS) for transmitting andreceiving data in a wireless communication system.

BACKGROUND ART

A mobile communication system has been developed to provide voiceservices while ensuring the activity of a user. However, the mobilecommunication system has been expanded to its region up to data servicesin addition to the voice. Today, the shortage of resources is caused dueto an explosive increase of traffic, and thus there is a need for a moreadvanced mobile communication system because users require higher speedservices.

Requirements for a next-generation mobile communication system basicallyinclude the accommodation of explosive data traffic, a significantincrease of a transfer rate per user, the accommodation of thesignificantly increased number of connection devices, very lowend-to-end latency, and high energy efficiency. To this end, research iscarried out on various technologies, such as dual connectivity, massivemultiple input multiple output (MIMO), in-band full duplex,non-orthogonal multiple access (NOMA), super broadband support, anddevice networking.

SUMMARY

The present disclosure provides a method of generating and transmittinga demodulation reference signal (DMRS) for transmitting and receivingdata.

The present disclosure further provides a method of determining alocation of a symbol to which a DMRS is mapped when a terminal receivesa plurality of DMRSs.

The present disclosure further provides a method of determining alocation of a symbol to which a DMRS is mapped when transmitting DMRSsof the number fewer than the maximum number of DMRSs determined by ahigher layer.

The present disclosure further provides a method of determining alocation of a symbol to which a DMRS for demodulating transmitted datais mapped before information related to mapping of a DMRS is transmittedfrom a base station.

The technical problem of this disclosure is not limited to theabove-described technical problems and the other technical problems willbe understood by those skilled in the art from the followingdescription.

A method in which a terminal transmits and receives data in a wirelesscommunication system includes receiving downlink control informationfrom a base station, wherein the downlink control information includessymbol information related to a last symbol of a downlink sharedchannel; receiving a first demodulation reference signal (DMSR) and atleast one second DMRS for demodulating downlink data; and receiving datathrough the downlink shared channel, wherein a symbol position to whichthe at least one second DMRS is mapped is determined according to thesymbol information.

Further, the method further includes obtaining number informationrepresenting the maximum number of symbols to which the at least onesecond DMRS is mapped from the base station, wherein the symbol positionis determined according to the symbol information and the numberinformation.

Further, when the at least one second DMRS is mapped to symbols of thenumber fewer than the maximum number, the at least one second DMRS ismapped to a symbol at the same location as a mapping position of thesecond DMRS having the fewer number as the maximum number of symbols towhich the DMRS is mapped.

Further, when the downlink shared channel is transmitted earlier thanhigher layer signaling, a maximum value of a symbol to which the atleast one second DMRS is mapped is set to a specific value.

Further, the symbol position is determined according to the specificvalue and the symbol information.

Further, when the at least one second DMRS is mapped to symbols of thespecific number or more, the symbol position is shifted according to aposition of a symbol to which the first DMRS is mapped.

Further, the number information is received through Radio ResourceControl (RRC) signaling.

A method in which a base station transmits and receives data in awireless communication system includes transmitting downlink controlinformation to a terminal, wherein the downlink control informationincludes symbol information related to a last symbol of a downlinkshared channel; transmitting a first demodulation reference signal(DMSR) and at least one second DMRS for demodulating downlink data; andtransmitting data through the downlink shared channel, wherein a symbolposition to which the at least one second DMRS is mapped is determinedaccording to the symbol information.

A terminal for transmitting and receiving data in a wirelesscommunication system includes a radio frequency (RF) module fortransmitting and receiving a radio signal; and a processor functionallyconnected to the RF module, wherein the processor is configured toreceive downlink control information from a base station, wherein thedownlink control information includes symbol information related to alast symbol of a downlink shared channel, to receive a firstdemodulation reference signal (DMSR) and at least one second DMRS fordemodulating downlink data, and to receive data through the downlinkshared channel, wherein a symbol position to which the at least onesecond DMRS is mapped is determined according to the symbol information.

According to the present disclosure, by determining a location of asymbol to which a DMRS is mapped according to the maximum number ofsymbols to which a DMRS is mapped and a physical channel in which dataare transmitted, scheduling flexibility of a base station can beincreased.

Further, according to the present disclosure, when a DMRS is set to thenumber fewer than the number set by higher layer signaling, by mappingthe DMRS to the same location as that of a preset value in which thenumber equal to the preset number of DMRSs is the maximum number, theDMRS can be efficiently mapped.

Further, according to the present disclosure, when the DMRS is set tothe number fewer than the number set by higher layer signaling, bymapping the DMRS to the same location as that of a preset value in whichthe number equal to the preset number of DMRSs is the maximum number,MU-MIMO is possible even between terminals having the maximum numberdifferent from that of symbols to which the DMRS is mapped.

Further, according to the present disclosure, by setting a location towhich a DMRS for demodulating transmitted data is to be mapped beforehigher layer signaling including information related to the DMRS istransmitted, before higher layer signaling is transmitted, thetransmitted data can be received and demodulated.

The effect of this disclosure is not limited to the above-describedeffects and the other effects will be understood by those skilled in theart from the following description.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included herein as apart of thedescription for help understanding the present disclosure, provideembodiments of the present disclosure, and describe the technicalfeatures of the present disclosure with the description below.

FIG. 1A to 1B are diagrams illustrating the structure of a radio framein a wireless communication system to which the present disclosure maybe applied.

FIG. 2 is a diagram illustrating a resource grid for a downlink slot ina wireless communication system to which the present disclosure may beapplied.

FIG. 3 is a diagram illustrating a structure of downlink subframe in awireless communication system to which the present disclosure may beapplied.

FIG. 4 is a diagram illustrating a structure of uplink subframe in awireless communication system to which the present disclosure may beapplied.

FIG. 5 is a diagram illustrating an example of the shape in which PUCCHformats are mapped to the PUCCH region of uplink physical resource blockin a wireless communication system to which the present disclosure maybe applied.

FIG. 6 is a diagram illustrating an example of a signal processingprocedure of an uplink shared channel, which is a transport channel in awireless communication system to which the present disclosure may beapplied.

FIG. 7 illustrates an example of a self-contained subframe structure towhich a method proposed in the present disclosure may be applied.

FIGS. 8 to 10B are diagrams illustrating an example of a method ofmapping a DMRS to which the present disclosure may be applied.

FIGS. 11A to 11D are diagrams illustrating an example of a method ofmapping a DMRS according to the number of additionally set DMRSsproposed in the present disclosure.

FIG. 12A to 12C are diagrams illustrating another example of a method ofmapping a DMRS according to the number of additionally set DMRSsproposed in the present disclosure.

FIG. 13A to 13B are diagrams illustrating an example of a method ofmapping a DMRS when demodulation references of the number smaller thanthe maximum number proposed in the present disclosure are set.

FIGS. 14A to 15C are diagrams illustrating another example of a methodof mapping a DMRS when demodulation references of the number smallerthan the maximum number proposed in the present disclosure are set.

FIGS. 16A to 18C are diagrams illustrating another example of a methodof mapping a DMRS proposed in the present disclosure.

FIGS. 19A to 20B are diagrams illustrating another example of a methodof mapping a DMRS proposed in the present disclosure.

FIG. 21 is a flowchart illustrating an example of a method oftransmitting and receiving data of a terminal proposed in the presentdisclosure.

FIG. 22 is a flowchart illustrating an example of a method oftransmitting and receiving data of a base station proposed in thepresent disclosure.

FIG. 23 is a diagram illustrating an example of an internal blockdiagram of a wireless device to which the present disclosure may beapplied.

FIG. 24 is a block diagram illustrating a configuration of acommunication device according to an embodiment of the presentdisclosure.

FIG. 25 is a diagram illustrating an example of an RF module of awireless communication device to which a method proposed in thisdisclosure may be applied.

FIG. 26 is a diagram illustrating another example of an RF module of awireless communication device to which a method proposed in thisdisclosure may be applied.

DETAILED DESCRIPTION

Reference will now be made in detail to the preferred embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. The detailed description set forth below inconnection with the appended drawings is a description of exemplaryembodiments and is not intended to represent the only embodimentsthrough which the concepts explained in these embodiments can bepracticed. The detailed description includes details for the purpose ofproviding an understanding of the present disclosure. However, it willbe apparent to those skilled in the art that these teachings may beimplemented and practiced without these specific details.

In some instances, known structures and devices are omitted, or areshown in a block diagram form focused on important features of thestructures and devices in order to avoid making obscure the concept ofthe present disclosure.

In this disclosure, abase station has a meaning as a terminal node of anetwork, directly communicating with a terminal. In this document, aspecific operation illustrated as being performed by a base station maybe performed by an upper node of the base station according tocircumstances. That is, it is evident that in a network includingmultiple network nodes including a base station, various operationsperformed for communication with a terminal may be performed by the basestation or other network nodes other than the base station. A “basestation (BS)” may be substituted with a term, such as a fixed station, aNode B, an evolved-NodeB (eNB), a base transceiver system (BTS), anaccess point (AP) or a transmission stage. Furthermore, a “terminal” maybe fixed or may have mobility, and may be substituted with a term, suchas a user equipment (UE), a mobile station (MS), a user terminal (UT), amobile subscriber station (MSS), a subscriber station (SS), an advancedmobile station (AMS), a wireless terminal (WT), a mMachine-typecommunication (MTC) device, a machine-to-machine (M2M) device, adevice-to-device (D2D) device, a reception stage or TRP(transmissionreception point).

Hereinafter, downlink (DL) refers to communication from a base stationto a UE, and uplink (UL) refers to communication from a UE to a basestation. In downlink, a transmitter may be part of abase station, and areceiver may be part of a UE. In uplink, a transmitter may be part of aUE, and a receiver may be part of a base station.

Specific terms used in the following description are provided to helpunderstanding of the present disclosure. The use of such specific termsmay be changed in other forms without departing from the technicalspirit of the present disclosure.

The following technology may be used in various wireless access systems,such as code division multiple access (CDMA), frequency divisionmultiple access (FDMA), time division multiple access (TDMA), orthogonalfrequency division multiple access (OFDMA), single carrier-FDMA(SC-FDMA), non-orthogonal multiple access (NOMA), and the like. The CDMAmay be implemented by radio technology universal terrestrial radioaccess (UTRA) or CDMA2000. The TDMA may be implemented by radiotechnology such as Global System for Mobile communications (GSM)/GeneralPacket Radio Service (GPRS)/Enhanced Data Rates for GSM Evolution(EDGE). The OFDMA may be implemented as radio technology such as IEEE802.11(Wi-Fi), IEEE 802.16(WiMAX), IEEE 802-20, E-UTRA (Evolved UTRA),and the like. The UTRA is a part of a universal mobile telecommunicationsystem (UMTS). 3rd generation partnership project (3GPP) long termevolution (LTE) as a part of an evolved UMTS (E-UMTS) using evolved-UMTSterrestrial radio access (E-UTRA) adopts the OFDMA in a downlink and theSC-FDMAin an uplink. LTE-advanced (A) is an evolution of the 3GPP LTE.

The embodiments of the present disclosure may be based on standarddocuments disclosed in at least one of IEEE 802, 3GPP, and 3GPP2 whichare the wireless access systems. That is, steps or parts which are notdescribed to definitely show the technical spirit of the presentdisclosure among the embodiments of the present disclosure may be basedon the documents. Further, all terms disclosed in the document may bedescribed by the standard document.

3GPP LTE/LTE-A is primarily described for clear description, buttechnical features of the present disclosure are not limited thereto.

General wireless communication system to which the present disclosuremay be applied

FIGS. 1A to 1B shows the structure of a radio frame in a wirelesscommunication system to which the present disclosure may be applied.

3GPP LTE/LTE-A supports a type 1 radio frame structure applicable tofrequency division duplex (FDD) and a type 2 radio frame structureapplicable to time division duplex (TDD).

In FIGS. TA to 1B, the size of the radio frame in the time domain isrepresented as a multiple of a time unit of T_s=T/(15000*2048). Downlinkand uplink transmission are configured with a radio frame having aperiod of T_f=307200*T_s=10 ms.

FIG. 1A illustrates the structure of the type 1 radio frame. The Type 1radio frame may be applied to both full duplex and half duplex FDD.

The radio frame includes 10 subframes. One radio frame includes 20 slotsof T_slot=15360*T_s=0.5 ms length. The slots are assigned indices from 0to 19. One subframe includes contiguous 2 slots in the time domain, anda subframe i includes a slot 2 i and a slot 2 i+1. The time taken totransmit one subframe is called a transmission time period (TTI). Forexample, the length of one subframe may be 1 ms, and the length of oneslot may be 0.5 ms.

In FDD, uplink transmission and downlink transmission are divided in thefrequency domain. There is no limit to full duplex FDD, whereas a userequipment cannot perform transmission and reception at the same time ina half duplex FDD operation.

One slot includes a plurality of orthogonal frequency divisionmultiplexing (OFDM) symbols in the time domain and includes multipleresource blocks (RBs) in the frequency domain. 3GPP LTE uses OFDMA indownlink, and thus an OFDM symbol is for representing one symbol period.An OFDM symbol may be called one SC-FDMA symbol or symbol period. Aresource block is a resource allocation unit, and includes a pluralityof contiguous subcarriers in one slot.

FIG. 1B shows the frame structure type 2.

A type 2 radio frame includes 2 half frames, each one having a length of153600*T_s=5 ms. Each half frame includes 5 subframes having a length of30720*T_s=1 ms.

In the frame structure type 2 of a TDD system, an uplink-downlinkconfiguration is a rule indicating whether uplink and downlink areallocated (or reserved) with respect to all subframes.

Table 1 shows an uplink-downlink configuration.

TABLE 1 Downlink- Uplink- to-Uplink Downlink Switch-point Subframenumber configuration periodicity 0 1 2 3 4 5 6 7 8 9 0  5 ms D S U U U DS U U U 1  5 ms D S U U D D S U U D 2  5 ms D S U D D D S U D D 3 10 msD S U U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D DD D 6  5 ms D S U U U D S U U D

Referring to Table 1, for each subframe of a radio frame, “D” indicatesa subframe for downlink transmission, “U” is a subframe for uplinktransmission, and “S” indicates a special subframe including threefields of a downlink pilot time slot (DwPTS), a guard period (GP), andan uplink pilot time slot (UpPTS).

The DwPTS is used for initial cell search, synchronization or channelestimation in a user equipment. The UpPTS is used to perform channelestimation in abase station and uplink transmission synchronization fora user equipment. The GP is a period for removing interference occurringin uplink due to the multi-path delay of a downlink signal betweenuplink and downlink.

Each subframe i includes a slot 2 i and a slot 2 i+1, each one having alength of T_slot=15360*T_s=0.5 ms.

An uplink-downlink configuration may be divided into 7 types. Theposition and/or number of downlink subframes, special subframes, uplinksubframes are different for each configuration.

A point of time switching from the downlink to the uplink or a point oftime switching from the uplink to the downlink is called a switchingpoint. Switching point periodicity means the period in which an aspectin which an uplink subframe and a downlink subframe switch isidentically repeated, and supports both 5 ms and 10 ms. In the case ofthe 5 ms downlink-uplink switching point periodicity, a special subframeS is present in each half-frame. In the case of the 5 ms downlink-uplinkswitching point periodicity, a special subframe S is present only in thefirst half-frame.

In all configurations, Nos. 0 and 5 subframe and a DwPTS are an intervalfor only downlink transmission. An UpPTS and a subframe subsequent to asubframe is always an interval for uplink transmission.

Such an uplink-downlink configuration is system information and may beknown to both a base station and a user equipment. The base station maynotify the user equipment of a change in the uplink-downlink allocationstate of a radio frame by transmitting only the index of configurationinformation whenever uplink-downlink configuration information ischanged. Furthermore, the configuration information is a kind ofdownlink control information and may be transmitted through a physicaldownlink control channel (PDCCH) like other scheduling information. Theconfiguration information is broadcast information and may betransmitted to all user equipments within a cell in common through abroadcast channel.

Table 2 shows the configuration of a special subframe (the length ofDwPTS/GP/UpPTS).

TABLE 2 Normal cyclic prefix in downlink Extended cyclic prefix indownlink UpPTS UpPTS Normal Extended Normal Extended Special cycliccyclic cyclic cyclic subframe prefix in prefix in prefix in prefix inconfiguration DwPTS uplink uplink DwPTS uplink uplink 0  6592 · T_(s)2192 · T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 119760 · T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 ·T_(s) 25600 · T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 ·T_(s) 5  6592 · T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 ·T_(s) 23040 · T_(s) 7 21952 · T_(s) — — — 8 24144 · T_(s) — — —

The structure of the radio frame according to the example of FIGS. 1A to1B is merely one example, and the number of subcarriers included in theradio frame or the number of slots included in a subframe or the numberof OFDM symbols included in a slot may be changed in various manners.

FIG. 2 is a diagram illustrating a resource grid for one downlink slotin the wireless communication system to which the present disclosure canbe applied.

Referring to FIG. 2 , one downlink slot includes the plurality of OFDMsymbols in the time domain. Herein, it is exemplarily described that onedownlink slot includes 7 OFDM symbols and one resource block includes 12subcarriers in the frequency domain, but the present disclosure is notlimited thereto.

Each element on the resource grid is referred to as a resource elementand one resource block includes 12×7 resource elements. The number ofresource blocks included in the downlink slot, N{circumflex over ( )}DLis subordinated to a downlink transmission bandwidth.

A structure of the uplink slot may be the same as that of the downlinkslot.

FIG. 3 illustrates a structure of a downlink subframe in the wirelesscommunication system to which the present disclosure can be applied.

Referring to FIG. 3 , a maximum of three former OFDM symbols in thefirst slot of the sub frame is a control region to which controlchannels are allocated and residual OFDM symbols is a data region towhich a physical downlink shared channel (PDSCH) is allocated. Examplesof the downlink control channel used in the 3GPP LTE include a PhysicalControl Format Indicator Channel (PCFICH), a Physical Downlink ControlChannel (PDCCH), a Physical Hybrid-ARQ Indicator Channel (PHICH), andthe like.

The PFCICH is transmitted in the first OFDM symbol of the subframe andtransports information on the number (that is, the size of the controlregion) of OFDM symbols used for transmitting the control channels inthe subframe. The PHICH which is a response channel to the uplinktransports an Acknowledgement (ACK)/Not-Acknowledgement (NACK) signalfor a hybrid automatic repeat request (HARQ). Control informationtransmitted through a PDCCH is referred to as downlink controlinformation (DCI). The downlink control information includes uplinkresource allocation information, downlink resource allocationinformation, or an uplink transmission (Tx) power control command for apredetermined terminal group.

The PDCCH may transport A resource allocation and transmission format(also referred to as a downlink grant) of a downlink shared channel(DL-SCH), resource allocation information (also referred to as an uplinkgrant) of an uplink shared channel (UL-SCH), paging information in apaging channel (PCH), system information in the DL-SCH, resourceallocation for an upper-layer control message such as a random accessresponse transmitted in the PDSCH, an aggregate of transmission powercontrol commands for individual terminals in the predetermined terminalgroup, a voice over IP (VoIP). A plurality of PDCCHs may be transmittedin the control region and the terminal may monitor the plurality ofPDCCHs. The PDCCH is constituted by one or an aggregate of a pluralityof continuous control channel elements (CCEs). The CCE is a logicalallocation wise used to provide a coding rate depending on a state of aradio channel to the PDCCH. The CCEs correspond to a plurality ofresource element groups. A format of the PDCCH and a bit number ofusable PDCCH are determined according to an association between thenumber of CCEs and the coding rate provided by the CCEs.

The base station determines the PDCCH format according to the DCI to betransmitted and attaches the control information to a cyclic redundancycheck (CRC) to the control information. The CRC is masked with a uniqueidentifier (referred to as a radio network temporary identifier (RNTI))according to an owner or a purpose of the PDCCH. In the case of a PDCCHfor a specific terminal, the unique identifier of the terminal, forexample, a cell-RNTI (C-RNTI) may be masked with the CRC. Alternatively,in the case of a PDCCH for the paging message, a paging indicationidentifier, for example, the CRC may be masked with a paging-RNTI(P-RNTI). In the case of a PDCCH for the system information, in moredetail, a system information block (SIB), the CRC may be masked with asystem information identifier, that is, a system information (SI)-RNTI.The CRC may be masked with a random access (RA)-RNTI in order toindicate the random access response which is a response to transmissionof a random access preamble.

PDCCH (Physical Downlink Control Channel)

Hereinafter, a PDCCH will be described in detail.

The control information transmitted via the PDCCH is referred to asdownlink control information (DCI). The size and use of controlinformation transmitted via the PDCCH may be changed according to DCIformat or the size of control information may be changed according tocoding rate.

Table 3 shows the DCI according to DCI format

TABLE 3 PUCCH Format Uplink Control Information(UCI) Format 1 SchedulingRequest(SR)(unmodulated waveform) Format 1a 1-bit HARQ ACK/NACKwith/without SR Format 1b 2-bit HARQ ACK/NACK with/without SR Format 2CQI (20 coded bits) Format 2 CQI and 1- or 2-bit HARQ ACK/NACK (20 bits)for extended CP only Format 2a CQI and 1-bit HARQ ACK/NACK (20 + 1 codedbits) Format 2b CQI and 2-bit HARQ ACK/NACK (20 + 2 coded bits)

Referring to Table 3 above, the DCI format includes format 0 forscheduling of a PUSCH, format 1 for scheduling of one PDSCH codeword,format 1A for compact scheduling of one PDSCH codeword, format 1 c forvery compact scheduling of a DL-SCH, format 2 for PDSCH scheduling in aclosed-loop spatial multiplexing mode, format 2A for PDSCH scheduling inan open-loop spatial multiplexing mode, formats 3 and 3A fortransmission of a transmission power control (TPC) command for an uplinkchannel, and format 4 for PUSCH scheduling in a uplink cell in amultiple antenna port transmission mode.

DCI format 1A may be used for PDSCH scheduling regardless of thetransmission mode of the UE.

Such DCI format is independently applicable per UE and PDCCHs of severalUEs may be multiplexed within one subframe. The PDCCH is composed of anaggregate of one or several control channel elements (CCEs). The CCE isa logical allocation unit used to provide a PDCCH with a coding rateaccording to radio channel state. The CCE refers to a unit correspondingto 9 sets of REGs composed of four resource elements. The BS may use {1,2, 4, 8} CCEs in order to configure one PDCCH signal and {1, 2, 4, 8} isreferred to as a CCE aggregation level.

The number of CCEs used to transmit a specific PDCCH is determined bythe BS according to channel state. The PDCCH configured according to UEis interleaved and mapped to a control channel region of each subframeby a CCE-to-RE mapping rule. The location of the PDCCH may depend on thenumber of OFDM symbols for a control channel of each subframe, thenumber of PHICH groups, transmit antenna, frequency shift, etc.

As described above, channel coding is performed independent of themultiplexed PDCCHs of the UEs and cyclic redundancy check (CRC) isapplied. A unique identifier (UE ID) of each UE is masked to the CRCsuch that the UE receives the PDCCH thereof. However, in the controlregion allocated within the subframe, the BS does not provide the UEwith information about where the PDCCH of the UE is located. Since theUE does not know the location of the PDCCH thereof and at which CCEaggregation level or with which DCI format the PDCCH thereof istransmitted, the UE monitors a set of PDCCH candidates within thesubframe to detect the PDCCH thereof, in order to receive the controlchannel from the BS. This is referred to as blind decoding (BD).

The BD may also be referred to as blind detection or blind detect. TheBD refers to a method of, at a UE, de-masking a UE ID thereof in a CRCportion, checking CRC errors, and determining whether a PDCCH is acontrol channel thereof.

Hereinafter, the information transmitted by DCI format 0 will bedescribed.

DCI format 0 is used for PUSCH scheduling in one uplink cell.

Table 4 represents the information transmitted through DCI format 0

TABLE 4 Format 0 (Release 8) Format 0 (Release 10) Carrier Indicator(CIF) Flag for format 0/format 1A Flag for format 0/format 1Adifferentiation differentiation Hopping flag (FH) Hopping flag (FH)Resource block assignment (RIV) Resource block assignment (RIV) MCS andRV MCS and RV NDI (New Data Indicator) NDI (New Data Indicator) TPC forPUSCH TPC for PUSCH Cyclic shift for DM RS Cyclic shift for DM RS ULindex (TDD only) UL index (TDD only) Downlink Assignment Index (DAI)Downlink Assignment Index (DAI) CSI request (1 bit) CSI request (1 or 2bits: 2 bit is for multi carrier) SRS request Resource allocation type(RAT)

Referring to Table 4 above, the following information is transmittedthrough DCI format 0.

1) Carrier indicator, which has a length of 0 or 3 bits.

2) Flag for DCI format 0 and DCI format 1A differentiation, which has alength of 1 bit, and 0 indicates DCI format 0 and 1 indicates DCI format1A

3) Frequency hopping flag, which has 1 bit. This field may used for themulti-cluster allocation for the Most Significant bit (MSB) of thecorresponding resource allocation if it is required.

4) Resource block assignment and hopping resource allocation, which has┌log₂(N_(RB) ^(DL)(N_(RB) ^(DL)+1)/2)┐ bit.

Herein, in the case of PUS CH hopping in a single-cluster allocation, inorder to acquire the value of ñ_(PRB)(i), the most significant bits(MSBs) of NUL_hop number are used. (┌log₂(N_(RB) ^(UL)(N_(RB)^(UL)+1)/2)┐−N_(UL_hop)) bit provides the resource allocation of thefirst slot in the uplink subframe. In addition, in the case that thereis no PUSCH hopping in the single-cluster allocation, (┌log₂(N_(RB)^(UL)(N_(RB) ^(UL)+1)/2)┐) bit provides the resource allocation in theuplink subframe. In addition, in the case that there is no PUSCH hoppingin a multi-cluster allocation, the resource allocation information isobtained from the concatenation between the frequency hopping flag fieldand the hopping resource allocation field of the resource blockallocation, and (┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐) bit providesthe resource allocation in the uplink subframe. In this case, value of Pis determined by the number of downlink resource blocks.

5) Modulation and coding scheme (MCS), which has a length of 1 bit.

6) New data indicator, which has a length of 2 bits.

7) Transmit Power Control (TPC) command for PUSCH, which has a length of2 bits.

8) Cyclic shift (CS) for a demodulation reference signal (DMRS) and anindex of orthogonal cover/orthogonal cover code (OC/OCC), which has 3bits.

9) Uplink index, which has a length of 2 bits. This field exits only forthe TDD operation according to uplink-downlink configuration 0.

10) Downlink Assignment Index (DAI), which has a length of 2 bits. Thisfield exits only for the TDD operation according to uplink-downlinkconfigurations 1-6.

11) Channel State Information (CSI) request, which has a length of 1 bitor 2 bits. Herein, the field of 2 bits is applied only to the case thatthe corresponding DCI is mapped to the UE to which one or more downlinkcells are configured by the Cell-RNTI (C-RNTI) in a UE-specific manner.

12) Sounding Reference Signal (SRS) request, which has a length of 0 bitor 1 bit. Herein, this field exists only in the case that the schedulingPUSCH is mapped by the C-RNTI in the UE-specific manner.

13) Resource allocation type, which has a length of 1 bit.

In the case that the number of information bits in DCI format 0 issmaller than the payload size (including additional padding bits) of DCIformat TA, 0 is added in order that DCI format TAbecomes identical toDCI format 0.

FIG. 4 illustrates a structure of an uplink subframe in the wirelesscommunication system to which the present disclosure can be applied.

Referring to FIG. 4 , the uplink subframe may be divided into thecontrol region and the data region in a frequency domain. A physicaluplink control channel (PUCCH) transporting uplink control informationis allocated to the control region. A physical uplink shared channel(PUSCH) transporting user data is allocated to the data region. Oneterminal does not simultaneously transmit the PUCCH and the PUSCH inorder to maintain a single carrier characteristic.

A resource block (RB) pair in the subframe are allocated to the PUCCHfor one terminal. RBs included in the RB pair occupy differentsubcarriers in two slots, respectively. The RB pair allocated to thePUCCH frequency-hops in a slot boundary.

Physical Uplink Control Channel (PUCCH)

The uplink control information (UCI) transmitted through the PUCCH mayinclude a scheduling request (SR), HARQ ACK/NACK information, anddownlink channel measurement information.

The HARQ ACK/NACK information may be generated according to a downlinkdata packet on the PDSCH is successfully decoded. In the existingwireless communication system, 1 bit is transmitted as ACK/NACKinformation with respect to downlink single codeword transmission and 2bits are transmitted as the ACK/NACK information with respect todownlink 2-codeword transmission.

The channel measurement information which designates feedbackinformation associated with a multiple input multiple output (MIMO)technique may include a channel quality indicator (CQI), a precodingmatrix index (PMI), and a rank indicator (RI). The channel measurementinformation may also be collectively expressed as the CQI.

20 bits may be used per subframe for transmitting the CQI.

The PUCCH may be modulated by using binary phase shift keying (BPSK) andquadrature phase shift keying (QPSK) techniques. Control information ofa plurality of terminals may be transmitted through the PUCCH and whencode division multiplexing (CDM) is performed to distinguish signals ofthe respective terminals, a constant amplitude zero autocorrelation(CAZAC) sequence having a length of 12 is primary used. Since the CAZACsequence has a characteristic to maintain a predetermined amplitude inthe time domain and the frequency domain, the CAZAC sequence has aproperty suitable for increasing coverage by decreasing apeak-to-average power ratio (PAPR) or cubic metric (CM) of the terminal.Further, the ACK/NACK information for downlink data transmissionperformed through the PUCCH is covered by using an orthogonal sequenceor an orthogonal cover (OC).

Further, the control information transmitted on the PUCCH may bedistinguished by using a cyclically shifted sequence having differentcyclic shift (CS) values. The cyclically shifted sequence may begenerated by cyclically shifting a base sequence by a specific cyclicshift (CS) amount. The specific CS amount is indicated by the cyclicshift (CS) index. The number of usable cyclic shifts may vary dependingon delay spread of the channel. Various types of sequences may be usedas the base sequence the CAZAC sequence is one example of thecorresponding sequence.

Further, the amount of control information which the terminal maytransmit in one subframe may be determined according to the number (thatis, SC-FDMA symbols other an SC-FDMA symbol used for transmitting areference signal (RS) for coherent detection of the PUCCH) of SC-FDMAsymbols which are usable for transmitting the control information.

In the 3GPP LTE system, the PUCCH is defined as a total of 7 differentformats according to the transmitted control information, a modulationtechnique, the amount of control information, and the like and anattribute of the uplink control information (UCI) transmitted accordingto each PUCCH format may be summarized as shown in Table 5 given below

TABLE 5 PUCCH Format Uplink Control Information(UCI) Format 1 SchedulingRequest(SR)(unmodulated waveform) Format 1a 1-bit HARQ ACK/NACKwith/without SR Format 1b 2-bit HARQ ACK/NACK with/without SR Format 2CQI (20 coded bits) Format 2 CQI and 1- or 2-bit HARQ ACK/NACK (20 bits)for extended CP only Format 2a CQI and 1-bit HARQ ACK/NACK (20 + 1 codedbits) Format 2b CQI and 2-bit HARQ ACK/NACK (20 + 2 coded bits)

PUCCH format 1 is used for transmitting only the SR. A waveform which isnot modulated is adopted in the case of transmitting only the SR andthis will be described below in detail.

PUCCH format 1 a or 1 b is used for transmitting the HARQ ACK/NACK.PUCCH format 1 a or 1 b may be used when only the HARQ ACK/NACK istransmitted in a predetermined subframe. Alternatively, the HARQACK/NACK and the SR may be transmitted in the same subframe by usingPUCCH format 1 a or 1 b.

PUCCH format 2 is used for transmitting the CQI and PUCCH format 2 a or2 b is used for transmitting the CQI and the HARQ ACK/NACK.

In the case of an extended CP, PUCCH format 2 may be transmitted fortransmitting the CQI and the HARQ ACK/NACK.

FIG. 5 a diagram illustrating one example of a type in which PUCCHformats are mapped to a PUCCH region of an uplink physical resourceblock in the wireless communication system to which the presentdisclosure can be applied.

In FIG. 5 , N_(RB) ^(UL) represents the number of resource blocks in theuplink and 0, 1, . . . , N_(RB) ^(UL)-1 mean numbers of physicalresource blocks. Basically, the PUCCH is mapped to both edges of anuplink frequency block. As illustrated in FIG. 5 , PUCCH format 2/2 a/2b is mapped to a PUCCH region expressed as m=0, 1 and this may beexpressed in such a manner that PUCCH format 2/2 a/2 b is mapped toresource blocks positioned at a band edge. Further, both PUCCH format2/2 a/2 b and PUCCH format 1/1 a/1 b may be mixed and mapped to a PUCCHregion expressed as m=2. Next, PUCCH format 1/1 a/1 b may be mapped to aPUCCH region expressed as m=3, 4, and 5. The number (N_(RB) ⁽²⁾) ofPUCCH RBs which are usable by PUCCH format 2/2 a/2 b may be indicated toterminals in the cell by broadcasting signaling.

PUCCH format 2/2 a/2 b is described. PUCCH format 2/2 a/2 b is a controlchannel for transmitting channel measurement feedback (CQI, PMI, andRI).

A reporting period of the channel measurement feedbacks (hereinafter,collectively expressed as CQI information) and a frequency wise(alternatively, a frequency resolution) to be measured may be controlledby the base station. In the time domain, periodic and aperiodic CQIreporting may be supported. PUCCH format 2 may be used for only theperiodic reporting and the PUSCH may be used for aperiodic reporting. Inthe case of the aperiodic reporting, the base station may instruct theterminal to transmit a scheduling resource loaded with individual CQIreporting for the uplink data transmission.

FIG. 6 is a diagram illustrating an example of a signal processingprocess of an uplink shared channel, which is a transport channel in awireless communication system to which the present disclosure may beapplied.

Hereinafter, a signal processing process of an uplink shared channel(hereinafter, referred to as “UL-SCH”) may be applied to one or moretransport channels or control information types.

Referring to FIG. 6 , the UL-SCH transmits data to a coding unit in theform of a transport block (TB) once every transmission time interval(TTI).

CRC parity bits p₀, p₁, p₂, p₃, . . . , p_(L-1) are attached to bits a₀,a₁, a₂, a₃, . . . , a_(A-1) of a transport block received from a higherlayer (S6010). In this case, A is a size of the transport block, and Lis the number of parity bits. Input bits to which the CRC is attachedare b₀, b₁, b₂, b₃, . . . , b_(B-1). In this case, B represents thenumber of bits of the transport block including the CRC.

b₀, b₁, b₂, b₃, . . . , b_(B-1) are segmented into a plurality of codeblocks (CBs) according to a TB size, and CRCs are attached to theplurality of divided CBs (S6020). After code block segmentation and CRCattachment, bits are c_(r0), c_(r1), c_(r2), c_(r3), . . . , c_(r(K)_(r) ⁻¹⁾. Here, r is the number (r=0, . . . , C−1) of code blocks, andKris the number of bits according to a code block r. Further, Crepresents the total number of code blocks.

Thereafter, channel coding is performed (S6030). Output bits afterchannel coding are d_(r0) ^((i)), d_(r1) ^((i)), d_(r2) ^((i)), d_(r3)^((i)), . . . , d_(r(D) _(r) ⁻¹⁾ ^((i)). In this case, i is an encodedstream index and may have a value of 0, 1, or 2. Dr represents thenumber of bits of i-th coded stream for the code block r. r is a codeblock number (r=0, . . . , C−1), and C represents the total number ofcode blocks. Each code block may be encoded by each turbo coding.

Thereafter, rate matching is performed (S6040). Bits after rate matchingare e_(r0), e_(r1), e_(r2), e_(r3), . . . , e_(r(E) _(r) ⁻¹⁾. In thiscase, r is the number (r=0, . . . , C−1) of code blocks, and Crepresents the total number of code blocks. Er represents the number ofrate matched bits of the r-th code block.

Thereafter, concatenation between code blocks is performed again(S6050). After concatenation of code blocks is performed, bits are f₀,f₁, f₂, f₃, . . . , f_(G-1). In this case, G represents the total numberof encoded bits for transmission, and when control information ismultiplexed with UL-SCH transmission, the number of bits used fortransmission of control information is not included.

When control information is transmitted in the PUSCH, channel coding isindependently performed in the control information CQI/PMI, RI, andACK/NACK (S6070, S6080, and S6090). Because different coded symbols areallocated for transmission of each control information, each controlinformation has a different coding rate.

In time division duplex (TDD), as an ACK/NACK feedback mode, two modesof ACK/NACK bundling and ACK/NACK multiplexing by a higher layerconfiguration are supported. For ACK/NACK bundling, an ACK/NACKinformation bit is configured with 1 bit or 2 bits, and for ACK/NACKmultiplexing, an ACK/NACK information bit is configured with 1 to 4bits.

After a concatenation step between code blocks at step S134,multiplexing of encoded bits f₀, f₁, f₂, f₃, . . . , f_(G-1) of UL-SCHdata and encoded bits q₀, q₁, q₂, q₃, . . . , q_(N) _(L) _(−Q) _(CQI)⁻¹. of CQI/PMI is performed (S12060). A multiplexed result of data andCQI/PMI is g₀, g₁, g₂, g₃, . . . , g_(H′−1). In this case, g_(i)(i=0, .. . , H′−1) denotes a column vector having a (Q_(m)·N_(L)) length.H=(G+N_(L)·Q_(CQI)) and H′=H/(N_(L)·Q_(m)). N_(L) denotes the number oflayers to which the UL-SCH transport block is mapped, and H denotes thetotal number of encoded bits allocated for UL-SCH data and CQI/PMIinformation in the N_(L) number of transport layers to which thetransport block is mapped.

Thereafter, the multiplexed data, CQI/PMI, separately channel-coded RI,and ACK/NACK are channel interleaved to generate an output signal(S6100).

MIMO (Multi-Input Multi-Output)

MIMO technology uses multiple transmitting (Tx) antennas and multiplereceiving (Rx) antennas, away from those which have been generally usedone transmit antenna and one receive antenna. In other words, MIMOtechnology is technology for increasing a capacity or improving aperformance by using multiple input/output antennas at a transmittingend or a receiving end of a wireless communication system. Hereinafter,“MIMO” will be referred to as “multi-input/output antenna”.

More specifically, multi-input/output antenna technology does not relyon one antenna path so as to receive one total message, and collects aplurality of pieces of data received through several antennas tocomplete total data. As a result, MIMO technology may increase a datarate within a specific system range and also increase a system rangethrough a specific data rate.

Next-generation mobile communication requires much higher data ratesthan conventional mobile communication and thus it is expected thatefficient MIMO technology is always required. In such a situation, MIMOcommunication technology is next generation mobile communicationtechnology that can be widely used in mobile communication UEs andrepeaters, and due to expansion of data communication, it is attractingattention as a technology that can overcome the transmission limit ofother mobile communication according to a limit situation.

Among various transmission efficiency improvement technologies currentlybeing studied, MIMO technology is currently receiving the most attentionas a method of dramatically improving a communication capacity and atransmission/reception performance without additional frequencyallocation or power increase.

Demodulation Reference Signal for PUSCH

A reference signal sequence r(m) for generating an uplink DMRS isgenerated by Equation 1 when transform precoding for a PUSCH is notallowed.

In this case, an example of a case in which transform precoding for aPUSCH is not allowed may be a case of generating a transmission signalof a CP-OFDM scheme.

$\begin{matrix}{{r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}} & \left\lbrack {{Equation}1} \right\rbrack\end{matrix}$

Here, c(i) means the pseudo-random sequence.

When a transmission precoder for the PUSCH is allowed, a referencesignal sequence r(m) may be generated by Equation 2.

r ^((p))(m)=r _(u,ν) ^((α))(m)  [Equation 2]

A DMRS of the generated PUSCH is mapped to a physical resource accordingto Type 1 or 2 given by higher layer parameters, as illustrated in FIGS.7 and 8 .

In this case, the DMRS may be mapped to a single symbol or a doublesymbol according to the number of antenna ports.

When transform precoding is not allowed, a reference signal sequencer(m) may be mapped to a physical resource by Equation 3.

$\begin{matrix}\begin{matrix}{a_{k,l}^{({p,\mu})} = {\beta_{DMRS}{{w_{f}\left( k^{\prime} \right)} \cdot {w_{t}\left( l^{\prime} \right)} \cdot {r\left( {{2m} + {k'} + m_{0}} \right)}}}} \\{k = \left\{ \begin{matrix}{k_{0} + {4m} + {2{k'}} + \Delta} & {{Configuration}\ {type}1} \\{k_{0} + {6m} + {k'} + \Delta} & {{Configuration}\ {type}2}\end{matrix} \right.} \\{{k^{\prime} = 0},1} \\{l = {\left\{ {l_{0},\overset{\_}{l}} \right\} + l^{\prime}}}\end{matrix} & \left\lbrack {{Equation}3} \right\rbrack\end{matrix}$

When transform precoding is allowed, the reference signal sequence r(m)may be mapped to a physical resource by Equation 4.

$\begin{matrix}\begin{matrix}{a_{k,l}^{({p,\mu})} = {\beta_{DMRS}{{w_{f}\left( k^{\prime} \right)} \cdot {w_{t}\left( l^{\prime} \right)} \cdot {r\left( {{2m} + {k'} + m_{0}} \right)}}}} \\{k = \left\{ \begin{matrix}{k_{0} + {4m} + {2{k'}} + \Delta} & {{Configuration}\ {type}1} \\{k_{0} + {6m} + {k'} + \Delta} & {{Configuration}\ {type}2}\end{matrix} \right.} \\{{k^{\prime} = 0},1} \\{l = {\left\{ {l_{0},\overset{\_}{l}} \right\} + l^{\prime}}}\end{matrix} & \left\lbrack {{Equation}4} \right\rbrack\end{matrix}$

In Equations 3 and 4, w_(f)(k′), w_(t)(l′), and Δ are given by Tables 6and 7.

A reference point for k is a bandwidth part in which a PUSCH istransmitted, and k₀ is a subcarrier of the lowest number of carrierresource blocks allocated for PUSCH transmission.

Quantity m₀ is the subcarrier difference between k₀ and a subcarrier 0in a carrier resource block 0.

Reference points for 1 and l₀ of a first DMRS symbol may vary dependingon a mapping type.

-   -   PUSCH mapping type A:    -   l may be defined relative to the start of the slot.    -   When the higher layer parameter UL-DMRS-typeA-pos is equal to 3,        l₀ is 3, otherwise l₀ is 2.    -   PUSCH mapping type B:    -   l may be defined relative to the start of the scheduled PUSCH        resources.    -   l₀ is 0.

Locations of additional DMRS symbols may be given by a last OFDM symbolused for the PUSCH in the slot according to 1′ and Tables 8 and 9.

A time domain index 1′ and supported antenna ports p may be given byTable 10. However, when a higher layer parameter UL-DMRS-len is ‘1’, asingle symbol DMRS may be used.

When a higher layer parameter UL-DMRS-len is 2, a single symbol or adouble symbol DMRS may be determined by associated DCI.

TABLE 6 w_(f) (k′) w_(t) (l′) p Δ k′ = 0 k′ = 1 l′ = 0 |l′| = 1 1000 0+1 +1 +1 +1 1001 0 +1 −1 +1 +1 1002 1 +1 +1 +1 +1 1003 1 +1 −1 +1 +11004 0 +1 +1 +1 −1 1005 0 +1 −1 +1 −1 1006 1 +1 +1 +1 −1 1007 1 +1 −1 +1−1

TABLE 7 w_(f) (k′) w_(t) (l′) p Δ k′ = 0 k′ = 1 l′ = 0 |l′| = 1 1000 0+1 +1 +1 +1 1001 0 +1 −1 +1 +1 1002 2 +1 +1 +1 +1 1003 2 +1 −1 +1 +11004 4 +1 +1 +1 +1 1005 4 +1 −1 +1 +1 1006 0 +1 +1 +1 −1 1007 0 +1 −1 +1−1 1008 2 +1 +1 +1 −1 1009 2 +1 −1 +1 −1 1010 4 +1 +1 +1 −1 1011 4 +1 −1+1 −1

TABLE 8 Position Additional DM-RS positions l of last PUSCH mapping typeA PUSCH mapping type B PUSCH UL-DMRS-add-pos UL-DMRS-add-pos symbol 0 12 3 0 1 2 3 ≤7 — — 8 — 7 — 9 — 9 6, 9 — 10 — 9 6, 9 — 11 — 9 6, 9 5, 8,— 11 12 — 11 7, 11 5, 8, — 11 13 — 11 7, 11 5, 8, — 11

TABLE 9 Position Additional DM-RS positions l of last PUSCH manning typeA PUSCH mapping type B PUSCH UL-DMRS-add-pos UL-DMRS-add-pos symbol 0 12 3 0 1 2 3 ≤7 — — 8 — — 9 — 8 — 10 — 8 — 11 — 8 — 12 — 10 — 13 — 10 —

TABLE 10 Supported antenna ports p DM-RS Configuration Configurationduration UL-DMRS-add-pos l′ type 1 type 2 single-symbol 0, 1, 2, 3 01000-1003 1000-1005 DM-RS double-symbol 0 0, 1 1000-1007 1000-1011 DM-RS

Demodulation Reference Signals for PDSCH

A reference signal sequence r(m) for generating a downlink DMRS isgenerated by Equation 5.

$\begin{matrix}{{r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}} & \left\lbrack {{Equation}5} \right\rbrack\end{matrix}$

Here, c(i) means the pseudo-random sequence.

A DMRS of the generated PDSCH is mapped to a physical resource accordingto a type 1 or 2 given by a higher layer parameter.

In this case, the reference signal sequence r(m) may be mapped to aphysical resource by Equation 6.

$\begin{matrix}\begin{matrix}{a_{k,l}^{({p,\mu})} = {\beta_{DMRS}{{w_{f}\left( k^{\prime} \right)} \cdot {w_{t}\left( l^{\prime} \right)} \cdot {r\left( {{2m} + {k'} + m_{0}} \right)}}}} \\{k = \left\{ \begin{matrix}{k_{0} + {4m} + {2{k'}} + \Delta} & {{Configuration}\ {type}1} \\{k_{0} + {6m} + {k'} + \Delta} & {{Configuration}\ {type}2}\end{matrix} \right.} \\{{k^{\prime} = 0},1} \\{l = {\left\{ {l_{0},\overset{\_}{l}} \right\} + l^{\prime}}}\end{matrix} & \left\lbrack {{Equation}6} \right\rbrack\end{matrix}$

In Equation 5, 1 is defined relative to the start of a slot, andw_(f)(k′), w_(t)(l′), and A are given by Tables 11 and 12.

A reference point for k is a bandwidth part in which a PDSCH istransmitted, and k₀ is a subcarrier of the lowest number of carrierresource blocks allocated for PDSCH transmission.

Quantity m₀ is the subcarrier difference between k₀ and subcarrier 0 ina carrier resource block 0.

Reference points for 1 and l₀ of a first DMRS symbol may vary dependingon a mapping type.

-   -   PDSCH mapping type A:    -   l may be defined relative to the start of the slot.    -   If the higher layer parameter DL-DMRS-typeA-pos is equal to 3,        l₀ is 3, otherwise l₀ is 2.    -   PDSCH mapping type B:    -   l may be defined relative to the start of the scheduled PDSCH        resources.    -   l₀ is 0.

Locations of additional DMRS symbols may be given by a last OFDM symbolused for the PUSCH in a slot according to 1′ and Tables 13 and 14.

A time domain index 1′ and supported antenna ports p may be given byTable 15.

-   -   When the higher layer parameter DL-DMRS-len is 1, a single        symbol DMRS may be used.    -   When the higher layer parameter DL-DMRS-len is 2, a single        symbol or a double symbol DMRS may be determined by associated        DCI.

TABLE 11 w_(f) (k′) w_(t) (l′) p Δ k′ = 0 k′ = 1 l′ = 0 l′ = 1 1000 0 +1+1 +1 +1 1001 0 +1 −1 +1 +1 1002 1 +1 +1 +1 +1 1003 1 +1 −1 +1 +1 1004 0+1 +1 +1 −1 1005 0 +1 −1 +1 −1 1006 1 +1 +1 +1 −1 1007 1 +1 −1 +1 −1

TABLE 12 w_(f) (k′) w_(t) (l′) p Δ k′ = 0 k′ = 1 l′ = 0 l′ = 1 1000 0 +1+1 +1 +1 1001 0 +1 −1 +1 +1 1002 2 +1 +1 +1 +1 1003 2 +1 −1 +1 +1 1004 4+1 +1 +1 +1 1005 4 +1 −1 +1 +1 1006 0 +1 +1 +1 −1 1007 0 +1 −1 +1 −11008 2 +1 +1 +1 −1 1009 2 +1 −1 +1 −1 1010 4 +1 +1 +1 −1 1011 4 +1 −1 +1−1

TABLE 13 Position Additional DM-RS positions l of last PDSCH manningtype A PDSCH mapping type B PUSCH UL-DMRS-add-pos UL-DMRS-add-pos symbol0 1 2 3 0 1 2 3 ≤7 — — 8 — 7 — 9 — 9 6, 9 — 10 — 9 6, 9 — 11 — 9 6, 9 5,8, — 11 12 — 11 7, 11 5, 8, — 11 13 — 11 7, 11 5, 8, — 11

TABLE 14 Additional DM-RS positions l Position PDSCH mapping type PDSCHmapping type of last A B PDSCH DL-DMRS-add-pos DL-DMRS-add-pos symbol 01 2 0 1 2 ≤7 — — 8 — — 9 — 8 — 10 — 8 — 11 — 8 — 12 — 10 — 13 — 10 —

TABLE 15 Single or Supported antenna ports p double symbol ConfigurationConfiguration DM-RS l′ type 1 type 2 single 0 1000-1003 1000-1005 double0, 1 1000-1007 1000-1011

Procedure of UE for Receiving PDSCH

When the UE detects a PDCCH having the configured DCI format, the UEshould decode the corresponding PDSCH as indicated by the correspondingDCI.

When the UE is configured to decode the PDCCH with the CRC scrambledwith C-RNTI, the UE should decode the PDCCH and the corresponding PDSCH.Scramble initialization of these PDSCHs is determined by C-RNTI.

The UE may derive the DMRS type for the PDSCH from the configured CPtype and DL-DMRS-config-type, which is a higher layer parameterindicating a configuration type of the DMRS, as illustrated in Table 16.

TABLE 16 Value of the DL-DMRS-config-type CP type DM-RS type Notavailable Normal Type 1 Type 1 Normal Type 1 Type 2 Normal Type 2 Notavailable Extended Type 1 Type 1 Extended Type 1 Type 2 Extended Notapplicable

When the UE is configured with an additional DMRS for the PDSCH byhigher layer parameters, multiple DMRS symbols may be transmitted.

The UE may assume that a DMRS port configured with higher layerparameters is quasi co-located (QCL) for delay spread, Doppler spread,Doppler shift, average gain, average delay, and spatial RX parameters.

When the UE is configured with a higher parameter of ‘DL-PTRS-present’,the UE may assume that the presence and pattern of a phase trackingreference signal (PTRS) antenna port are a function of a correspondingscheduled MCS and a scheduled bandwidth.

When the UE is configured with higher layer parameters ‘dmrs-group2’ and‘DL-PTRS-present’, the UE may assume that a PTRS antenna port number isrelated to DMRS antenna ports indicated in a ‘dmrs-group 2’configuration for TBD of the associated parameters.

When the UE is configured with the higher layer parametersDL-PTRS-present and dmrs-group2, the PT-RS port may be related to aDM-RS antenna port of the lowest index among the configured DM-RSantenna ports indicated in the dmrs-group2 configuration for the PDSCH.

FIG. 7 is a diagram illustrating a self-contained subframe structure ina wireless communication system in which the present disclosure may beapplied.

In order to minimize data transmission latency in a TDD system, fifthgeneration (5G) new RAT considers a self-contained subframe structure,as illustrated in FIG. 4 .

In FIG. 7 , a hatched area (symbol index 0) represents a downlink (DL)control area, and a black portion (symbol index 13) represents an uplink(UL) control area. An area having no shaded display may be used for DLdata transmission or may be used for UL data transmission. Acharacteristic of such a structure is that DL transmission and ULtransmission proceed sequentially in one subframe and thus DL data maybe transmitted in a subframe, and UL ACK/NACK may also be received. As aresult, in case of a data transmission error, the time required for dataretransmission is reduced, thereby minimizing latency of final datatransmission.

In such a self-contained subframe structure, a time gap is required fora process in which the base station and the UE switch from atransmission mode to a reception mode or switch from a reception mode toa transmission mode. For this reason, some OFDM symbols at the time ofswitching from DL to UL in a self-contained subframe structure are setto a guard period (GP).

FIG. 8 is a diagram illustrating an example of a method of mapping aDMRS to which the present disclosure may be applied.

Referring to FIG. 8 , locations in which a front-load DMRS and anadditional DMRS are mapped to a second DMRS may be variable.

Specifically, when the subframe has an OFDM symbol for another purposeother than the OFDM symbol for downlink data transmission in onesubframe (or slot), as in a self-contained subframe structureillustrated in FIG. 7 , whether to set the additional DMRS and aposition thereof may be determined according to a structure of thesubframe.

For example, when the structure of the subframe is seven symbol slots,an additional DMRS is not transmitted and only a front-load DMRS may besupported, and when the structure of the subframe is configured with 14symbol slots, only the front-load DMRS may be supported or both afront-load DMRS and an additional DMRS may be supported.

Specifically, a location of a time axis OFDM symbol to which additionalDMRSs are mapped may be determined according to at least one of aconfiguration of a DL/UL slot, a slot type, or a slot structure.

That is, as illustrated in FIG. 8 , in the self-contained subframestructure, additional DMRSs may have different locations of OFDM symbolsmapped according to a guard segment and an area of the PUSCH.

For example, in the case of a self-contained subframe, a subframestructure may vary according to a guard segment and PUCCH and PUSCHsegments.

In this way, when the structure of the subframe is changed, ininterpolation of channels in a time domain, when a time axis location ofthe additional DMRS is set to the same location irrespective of thesubframe structure, a segment of extrapolation is extended and thus achannel estimation performance may be degraded.

Therefore, in order to estimate a changing channel in the time domain,an additional DMRS may be variably mapped to an OFDM symbol according tothe structure of a subframe.

FIG. 9A to D illustrate an example of a pattern of a DMRS proposed inthe present disclosure.

Referring to FIGS. 9A to 9D, a DMRS for estimating a channel may bemapped to one symbol or two symbols according to the number of antennapods.

Specifically, an uplink DMRS and a downlink DMRS may be generated by thefollowing method and mapped to resource areas. FIGS. 9(a) and 9(b)illustrate an example of an uplink or downlink DMRS mapped to a physicalresource according to a type 1, and FIGS. 9(c) and 9(d) illustrate anexample of an uplink or downlink DMRS mapped to a physical resourceaccording to a type 2.

A DMRS for demodulating uplink data or downlink data is generated bymapping a demodulation reference sequence to an OFDM symbol.

The DMRS sequence may be mapped to one or two OFDM symbols according toa mapping type, as illustrated in FIGS. 18A to 19B, and a CDM scheme maybe applied for port multiplexing.

FIGS. 10A to 10B are diagrams illustrating an example of a DMRS portindexing method proposed in the present disclosure.

As illustrated in FIGS. 10A to 10B, DMRS port indexing may varyaccording to a mapping type of a DMRS.

Specifically, when a mapping type of a DMRS is the above-described type1, DMRS port indexing is illustrated in FIG. 10A and Table 17.

TABLE 17 Port indexing Frequency offset: delta FD-OCC XX0 0 +1 +1 XX1 0+1 −1 XX2 1 +1 +1 XX3 0 +1 −1

When a mapping type of a DMRS is the above-described type 2, DMRS portindexing is illustrated in FIG. 10B and Table 18.

TABLE 18 Port Frequency indexing offset: delta FD-OCC XX0 0 +1 +1 XX1 0+1 44444444444444444444444444444444555555-   1 XX2 2 +1 +1 XX3 2 +1 −1XX4 4 +1 +1 XX5 4 +1 −1

QCL (Quasi-Co Location)

The antenna port is defined so that a channel in which a symbol on theantenna port is carried may be inferred from a channel in which anothersymbol on the same antenna port is carried. When a property of a channelfor carrying a symbol on one antenna port is deduced from a channel forcarrying a symbol on another antenna port, it may be regarded that twoantenna ports are in a quasi co-located or quasi co-location (QC/QCL)relationship.

Here, the channel characteristics may include one or more of delayspread, Doppler spread, frequency shift, average received power,received timing, and spatial RX parameter. Here, the spatial Rxparameter means a spatial (receiving) channel characteristic parametersuch as an angle of arrival.

In order to decode a PDSCH according to a detected PDCCH having intendedDCI for the UE and a given serving cell, the UE may be set to a list ofthe M number of TCI-State configurations in a higher layer parameterPDSCH-Config. The M depends on an UE capability.

Each TCI-State includes a parameter for configuring a quasi co-locationrelationship between one or two DL reference signals and a DM-RS port ofa PDSCH.

The quasi co-location relationship is set to a higher layer parameterqcl-Type1 for a first DL RS and qcl-Type2 (when it is set) for a secondDL RS.

In the case of two DL RSs, the QCL type is not the same regardless ofwhether the reference is the same DL RS or a different DL RS.

The quasi co-location type corresponding to each DL RS is given by ahigher layer parameter qcl-Type of QCL-Info and may take one of thefollowing values:

-   -   ‘QCL-TypeA’: {Doppler shift, Doppler spread, average delay,        delay spread}    -   ‘QCL-TypeB’: {Doppler shift, Doppler spread}    -   ‘QCL-TypeC’: {Doppler shift, average delay}    -   ‘QCL-TypeD’: {Spatial Rx parameter}

For example, when a target antenna port is a specific NZP CSI-RS, thecorresponding NZP CSI-RS antenna ports may be indicated/set to be QCL toa specific TRS from a QCL-Type A viewpoint and a specific SSB from aQCL-Type D viewpoint. The UE, having received such indication/settingmay receive the corresponding NZP CSI-RS using Doppler and delay valuesmeasured in the QCL-TypeA TRS and apply a reception beam used forreceiving a QCL-TypeD SSB to the corresponding NZP CSI-RS reception.

The UE receives an activation command used for mapping up to eight TCIstates to a codepoint of DCI field ‘Transmission ConfigurationIndication’.

One of functions of DCI is to transmit scheduling information of adownlink, an uplink, or a side link to the UE. A plurality of DCIformats are defined according to information transmitted to the UE, andin order to transmit specific information, a plurality of DCI formats isdefined according to information to be transmitted to a plurality ofUEs, and the DCI format defines many fields that transfer specificinformation.

The base station loads different information to each field of the DCI totransfer the different information to the UE. The UE may receive a fielddefined to the DCI format of the PDCCH, decode the field, and receiveinformation related to an operation to be performed by the UE, such asscheduling information.

Accordingly, the UE may perform an operation such as reception of data.

For example, in the case of DCI format 2D, a field (hereinafter,referred to as DCI field 1) meaning information about antenna ports,scrambling identification, and the number of layers, and a field(hereinafter, referred to as DCI field 2) meaning information aboutPDSCH RE Mapping and Quasi-Co-Location Indicators may be defined.

First, the UE may receive information of the DCI field 1 from the basestation to detect information about the number of entire layers using bythe base station for data transmission and a port index for transmittingthe corresponding data.

By receiving information of the DCI field 2, it is possible to detectthe information about the CSI-RS resource in a QCL relationship withports used for data transmission detected through the DCI field 1.

The CSI-RS resource information may be previously set to the UE throughhigher layer signaling, and a QCL relationship between a port in whichdata are transmitted and the CSI-RS resource may be flexibly set to theUE through DCI signaling.

The UE may obtain a value of second statistical information (e.g., delayspread, Doppler spread) of a channel that may help improve a performancein channel estimation for each CSI-RS resource.

Therefore, it is possible to recognize a CSI-RS resource in a QCLrelationship with antenna ports set through a DCI field 1 based on theinformation indicated by a DCI field 2, and by using secondarystatistical characteristics of a data transport channel between the basestation and the UE based on the CSI-RS resource in the channelestimation step, a channel estimation performance can be improved.

Further, the UE may recognize whether single TRP transmission or doubleTRP transmission (e.g., Comp (NCJT)) is performed through QCLinformation indicated by the DCI field 2.

For example, when one CSI-RS resource is indicated, the UE may assumesingle TRP transmission, and when two CSI-RS resources are indicated,the UE may assume double TRP transmission (i.e., Comp (NCJT)).

When a QCL relationship should be established between antenna portsmultiplexed through a CDM method in a frequency domain, a problem mayoccur in a relationship between the DCI field 1 and the DCI field.

An index of the antenna port related to the number of transmissionlayers in the DCI field 1 is fixed. In this case, when a QCLrelationship is not established between the antenna ports multiplexed bythe CDM method in the frequency domain, there is no QCL restriction on amultiplexing scheme and thus different QCL indications (e.g., single TRPtransmission/double TRP transmission) is possible through a DCI field 2.

As described above, in NR, DMRSs are classified into a front-load DMRSand an additional DMRS. In order to secure a fast decoding rate, thefront-load DMRS defines the DMRS in units of OFDM symbols and may belocated at a front symbol among OFDM symbols configuring a PDSCH or aPUSCH.

The additional DMRS may be used for estimating a channel varying to atime domain for time-varying channels due to Doppler spread, Dopplershift, etc. along with the front-load DMRS.

The front-load DMRS may be defined to a 1-symbol front-load DMRS and a2-symbol front-load DMRS according to the number of configuring OFDMsymbols and be set to the UE through higher layer signaling or downlinkcontrol information (DCI) signaling.

Further, the additional DMRS may be referred to as a 1-symbol additionalDMRS when defined together with the 1-symbol front-load DMRS and as a2-symbol additional DMRS when defined together with the 2-symbolfront-load DMRS.

The number and locations that may be defined for the two additionalDMRSs may be defined as illustrated in Tables 17 and 18.

Table 19 illustrates an example of a 1-symbol additional DMRS (startingfrom the 0th symbol).

TABLE 19 Position of the One 1-symbol Two 1-symbol Three 1-symbol lastPDSCH additional DMRS additional DMRS additional DMRS 13^(th) 11^(th)7^(th), 11^(th) 5^(th), 8^(th), 11^(th) 12^(th) 11^(th) 7^(th), 11^(th)5^(th), 8^(th), 11^(th) 11^(th)  9^(th) 6^(th), 9^(th) 5^(th), 8^(th),11^(th) 10^(th)  9^(th) 6^(th), 9^(th) N/A  9^(th)  9^(th) 6^(th),9^(th) N/A  8^(th)  7^(th) N/A N/A

Table 20 illustrates an example of a 2-symbol additional DMRS (startingfrom a 0th symbol).

TABLE 20 Position of the One 2-symbol Two 2-symbol Three 2-symbol lastPDSCH additional DMRS additional DMRS additional DMRS 13^(th) 10^(th),11^(th) N/A N/A 12^(th) 10^(th), 11^(th) N/A N/A 11^(th) 8^(th), 9^(th)N/A N/A 10^(th) 8^(th), 9^(th) N/A N/A  9^(th) 8^(th), 9^(th) N/A N/A 8^(th) N/A N/A N/A

In the case of Tables 19 and 20, when the front-load DMRS is located atsecond and third (starting from the 0th) OFDM symbols in the slot, allthereof may be applied. However, in the case of three 1-symboladditional DMRSs, only when the front-load DMRS is located at the secondOFDM symbol in the slot, a DMRS may be set at a position illustrated inTable 17, and when the front-load DMRS is located at the third OFDMsymbol, a location of the DMRS is not defined.

Accordingly, the present disclosure proposes a method of setting alocation of an additional DMRS according to a location of the front-loadDMRS in the case of three 1-symbol additional DMRSs.

Embodiments described hereinafter are merely divided for convenience ofdescription, and some components or characteristics of one embodimentmay be included in another embodiment or may be replaced withcorresponding components or characteristics of another embodiment.

For example, contents on setting of a location of an additional DMRSdescribed in Embodiment 1 may be commonly applied to various embodimentsof the present disclosure.

Hereinafter, in the present disclosure, the number of DMRSs may beinterpreted as the number of OFDM symbols to which the DMRSs are mapped.

Embodiment 1

FIG. 11 is a diagram illustrating an example of a method of mapping aDMRS according to the number of additionally set DMRSs proposed in thepresent disclosure.

Referring to FIG. 11 , when an additional DMRS is mapped to the specificnumber or more of ODFM symbols and is set to the UE, a location of theadditional DMRS may be changed according to the location of thefront-load DMRS.

Specifically, when the number of the additional DMRS is set to the UE asmore than the specific number (e.g., three), a location of theadditional DMRS may be changed to be set to the UE according to thelocation of the OFDM symbol to which the front-load DMRS is mapped.

In this case, the front-load DMRS and the additional DMRS may betogether set in a specific time domain (e.g., slot) set for datatransmission and reception to the UE, and when a location of thefront-load DMRS is differently set, a location of the OFDM symbol towhich the additional DMRS is mapped may also be changed and set.

For example, a location of the additional DMRS may be changed and set bya change amount in which a location of the front-load DMRS is changed(e.g., the number of OFDM symbols).

In Embodiment 1, “a case in which the number of additional DMRSs is setto the UE as more than the specific number” may be interpreted as a casein which a density of DMRSs is high in the time domain. Further, thefront-load DMRS and the additional DMRS are not separately referred to,and both may be referred to as a DMRS.

Therefore, Embodiment 1 may be interpreted as a method of setting a DMRSpattern to which the DMRSs are mapped when a DMRS pattern has a highdensity in the time domain.

When DMRS patterns of the front-load DMRS and the additional DMRS areset to the UE using Embodiment 1, a rule may be defined in which thebase station notifies a DMRS pattern to the UE through a predefinedsignal (e.g., a physical layer signal or a higher layer signal) or aDMRS pattern of an additional DMRS according to mapping of thefront-load DMRS between the base station and the UE may be fixedlyapplied.

Embodiment 1 is a method of setting a position of an OFDM symbol towhich additional DMRSs are mapped according to a change in a location ofan OFDM symbol to which a front-load DMRS is mapped, which may beapplied as a method of setting a DMRS pattern according to an area of anOFDM symbol in which a PDCCH may be set.

For example, when an area in which the PDCCH may be set is maximum twoOFDM symbols and maximum three OFDM symbols, Embodiment 1 may be appliedto a method of setting a DMRS pattern according to a time domain densityof the DMRS.

In Embodiment 1, the method of changing a location of the additionalDMRS according to a change amount of a location of the front-load DMRShas been described, but this may be applied to the following method.

When the number of additional DMRSs is set to the specific number ormore of UEs, the number of OFDM symbols that perform extrapolation maybe set to a specific number (e.g., one) or less.

When the number of additional DMRSs is set to a specific number or moreof UEs, the DMRS location may be set such that the number of OFDMsymbols that perform interpolation is smaller than or equal to thenumber of OFDM symbols that perform extrapolation.

In this case, extrapolation may mean an OFDM symbol located outside theOFDM symbol to which the DMRS is mapped. That is, the number of OFDMsymbols that perform extrapolation may mean the number of OFDM symbolsbefore the first DMRS or the number of OFDM symbols after the last DMRS.Further, interpolation may mean OFDM symbols located inside an OFDMsymbol to which DMRSs are mapped. That is, the number of OFDM symbolsthat perform interpolation may mean the number of OFDM symbols locatedbetween DMRSs.

FIGS. 11A and 11B illustrate an example of a setting method in which thelocation of an additional DMRS is fixed regardless of a location of afront-load DMRS.

In FIGS. 11A and 11B, while the front-load DMRS moves from a symbol 2 toa symbol 3, an DMRS segment located at symbols 3 and 5 is reduced,whereas a last DMRS is located to a symbol 11 and thus a segment ofextrapolation is long by two symbols.

In this way, in a case which the number of the additional DMRS is set to3, when a location of the additional DMRS is fixed regardless of alocation of the front-load DMRS, if a location of the front-load DMRS ischanged, as illustrated in FIGS. 11A and 11B, an extrapolation area maybe set larger than a segment between the front-load DMRS and the firstadditional DMRS, and a channel estimation performance may be degradeddue to the time-varying channel in the extrapolation area.

When the number of additional DMRSs is set to 3, it has an object forsupporting a very high speed UE and thus channel estimation due to thetime-varying channel is more important, and thus an optimized symbollocation of an optimized DMRS that may appropriately estimate thechannel should be considered.

Therefore, when a location of the front-load DMRS is changed asillustrated in FIGS. 11C and 11D, a position of an additional DMRS isthus changed and thus a channel estimation performance can be improveddue to the time-varying channel in an extrapolation area.

That is, in FIGS. 11C and 11D, when the front-load DMRS moves from asymbol 2 to a symbol 3, the additional DMRS may be moved and set by oneOFDM symbol.

In this case, because the extrapolation area may be reduced whilemaintaining the same interpolation area, a time-varying estimationperformance of the channel can be improved.

Embodiment 1-2

As an area in which the PDCCH may be set is set to maximum three OFDMsymbols or more, when a position of the front-load DMRS is set after anarea in which the PDCCH is set, the base station may set to the UE asthe maximum setting number of additional DMRSs to a specific number x(e.g., two) symbols.

After an area in which the PDCCH may be set is set to maximum 2 OFDMsymbols or less, when a position of the front-load DMRS is set, x may beset to a value smaller than or equal to the number y (e.g., 3) ofmaximum additional DMRSs that may be set.

In this case, an area capable of transmitting data in a slot may varyaccording to an area in which a PDCCH may be set. The larger area inwhich the PDCCH may be set may mean that an area for transmitting databecomes smaller.

In this case, an RS overhead may increase due to an additional DMRS.Therefore, by varying the number of additional DMRSs that may be setaccording to a size of an area in which the PDCCH may be set, an RSoverhead may be prevented from excessively increasing.

Further, when using Embodiment 1-2, by reducing the number of DMRSpatterns that may be defined between the base station and the UE,implementation complexity of the UE can be reduced.

Embodiment 1-3

FIGS. 12A to 12C are diagrams illustrating another example of a methodof mapping a DMRS according to the number of additionally set DMRSsproposed in the present disclosure.

Referring to FIGS. 12A to 12C, when the number of additional DMRSs isset to the UE as a specific number x (e.g., 3) or more, a position of alast additional DMRS may be set to be transmitted to a last symbol amongOFDM symbols set to data transmission.

Specifically, as illustrated in FIGS. 13A to 13B, when the number ofadditional DMRSs is set to ‘x’ or more, it may be an object forsupporting a very high speed UE.

Therefore, in this case, time-varying estimation of the channel is moreimportant, and an OFDM symbol position of an optimized DMRS capable ofappropriately estimating it should be considered.

Therefore, in order to prevent extrapolation having a greater effect onchannel estimation performance degradation, by setting a location of thelast additional DMRS to a last symbol among OFDM symbols set to datatransmission, an extrapolation area may not be generated.

In the case of Embodiment 1-3, because a location of an additional DMRSis set so that an extrapolation area does not occur, degradation of achannel estimation performance can be prevented due to the time-varyingchannel in the extrapolation area.

Because Embodiments 1 to 1-3 may be included as one of implementationmethods of the present disclosure, it is obvious that it may be regardedas a kind of proposed schemes. Further, the above-described schemes ofEmbodiments 1 to 1-3 may be implemented independently, but may beimplemented in a combination (or merge) form of some proposed schemes.

In information for applying the proposed methods (or information on therules of the proposed methods), a rule may be defined so that the basestation notifies through a predefined signal (e.g., a physical layersignal or a higher layer) to the UE or the transmitting UE notifiesthrough a predefined signal (e.g., a physical layer signal or a higherlayer) to the receiving UE.

In a specific example of the proposal, even when only the case of DL orUL is illustrated, the present proposal may be applied to all cases ofDL/UL, unless it is specified that the technical application is limitedto DL or UL.

Further, the proposed method is not limited only to uplink or downlinkcommunication, and the proposed method may be applied to directcommunication between UEs, a base station, a vehicle, a relay node, andthe like.

The Actual Number and Location of Transmitted DMRS in a Given SlotFormat

Positions of a 1-symbol front-load DMRS and a 2-symbol additional DMRSmay be defined as illustrated in Tables 19 and 20, respectively.

As illustrated in Tables 19 and 20, a position of a last PDSCH that maybe defined according to the number of additional DMRSs may be different.In this case, the position of the last PDSCH may mean symbol informationrelated to a last symbol of the downlink shared channel.

That is, the position of the last PDSCH may mean a position of a lastOFDM symbol to which the downlink data may be transmitted or may meanduration of the PDSCH for data transmission.

Portions corresponding to N/A in Tables 19 and 20 represent portions inwhich a DMRS pattern is not defined due to problems such as an RSoverhead.

In Tables 19 and 20, symbol information “Position of last PDSCH Symbol”may be dynamically set to the UE through DCI, and the number of presetadditional DMRSs may be set to the UE through higher layer signaling(e.g., RRC signaling).

In this case, when the number of additional DMRSs set through higherlayer signaling may not be defined in the “Position of last PDSCHsymbol” that is flexibly set, there is a need to define an operationbetween the base station and the UE for a portion corresponding to N/Ain Tables 19 and 20.

Accordingly, hereinafter, when the number of additional DMRSs setthrough higher layer signaling may not be defined in the position oflast PDSCH symbol (hereinafter, referred to as symbol information) thatis flexibly set, an operation between the UE and the base station isproposed.

Embodiment 2

The base station may set a specific value of symbol information that cansupport the number of additional DMRSs semi-statically set to the UEthrough higher layer signaling to the UE.

For example, in the case of one 1-symbol additional DMRS in Tables 19and 20, the symbol information may set one of values corresponding to8th, 9th, 10th, 11th, 12th, and 13th to an undefined N/A value.

Further, in the case of two 1-symbol additional DMRS, the symbolinformation may set one of values corresponding to 9th, 10th, 11th,12th, and 13th to an undefined N/A value.

That is, the base station may set one of values defined through higherlayer signaling to the UE as an undefined N/A value.

When using such a method, the UE may assume that symbol information thatmay not be supported by the number of additional DMRSs set throughhigher layer signaling is not set from the base station and thus thereis no need to define a separate operation for the corresponding case andcomplexity may be thus reduced.

Further, as in the following description, an operation may be definedbetween the base station and the UE such that symbol information inwhich the number of additional DMRSs set to the UE through higher layersignaling is not defined is set to the UE.

That is, symbol information in which the number of additional DMRSs setto the UE through higher layer signaling is not supported may correspondto a case in which there are few OFDM symbols allocated to a datachannel.

In this case, in order to reduce an RS overhead because the RS overheadis larger even if the same additional DMRS number is set, a method offlexibly switching with the smaller number of additional DMRSs may beapplied.

When using such a method, the number of OFDM symbols allocated to thedata channel is small and thus even if the smaller number of additionalDMRSs are used, time-varying of a channel may be estimated.

Embodiment 3

FIGS. 13A to 13B are diagrams illustrating an example of a method ofmapping a DMRS when demodulation references of the number smaller thanthe maximum number proposed in the present disclosure are set.

Referring to FIGS. 13A to 13B, when the number of additional DMRSs setthrough higher layer signaling may not be supported, additional DMRSsdefined after a last OFDM symbol by symbol information may not betransmitted.

Specifically, when the number of additional DMRSs set through higherlayer signaling may not be supported, i.e., when a location of a lastOFDM symbol of a PDSCH defined by symbol information is a symbol beforea last location of the additional DMRS, the last additional DMRS may notbe transmitted.

For example, when the number of additional DMRSs is set to three throughhigher layer signaling and the additional DMRSs are located at 5th, 8th,and 11th OFDM symbols, respectively, and as illustrated in FIG. 13A,when a location of a last PDSCH is a 13th OFDM symbol by symbolinformation, all preset addition DMRS may be transmitted. However, asillustrated in FIG. 13B, when a location of the last PDSCH is a 10thOFDM symbol by the symbol information, an additional DMRS of an 11thOFDM symbol is not transmitted.

Table 21 illustrates an example of a 1-symbol additional DMRS.

TABLE 21 Position of the One 1-symbol Two 1-symbol Three 1-symbol lastPDSCH additional DMRS additional DMRS additional DMRS 13^(th) 11^(th)7^(th), 11^(th) 5^(th) 12^(th) 11^(th) 7^(th), 11^(th) 5^(th) 11^(th) 9^(th) 6^(th), 9^(th) 5^(th) 10^(th)  9^(th) 6^(th), 9^(th) 5^(th),8^(th)  9^(th)  9^(th) 6^(th), 9^(th) 5^(th), 8^(th)  8^(th)  7^(th)6^(th) 5^(th), 8^(th)

As illustrated in Table 21, values that were N/A in Tables 19 and 20 maybe defined to specific values.

In this case, when the specific value is defined to a definite value orcorresponds to a specific condition, the UE and the base station may bedefined to operate according to a corresponding rule.

Embodiment 4

FIGS. 14 and 15 are diagrams illustrating another example of a method ofmapping a DMRS when demodulation references of the number smaller thanthe maximum number proposed in the present disclosure are set.

Referring to FIGS. 14 and 15 , when the number of additional DMRSs setthrough higher layer signaling may not be supported, additional DMRSsmay be transmitted to locations of the maximum number of additionalDMRSs that may be defined according to symbol information.

Specifically, the number of additional DMRS set through higher layersignaling transmitted from the base station to the UE may not besupported according to the number of symbols set by symbol information.

For example, when the number of additional DMRSs set through higherlayer signaling in Table 17 is 3, additional DMRSs are mapped to 5th,8th, and 11th OFDM symbols and transmitted.

However, when a location of the last PDSCH is set to an OFDM symbolsmaller than a 9th OFDM symbol or when the number of symbols to whichthe PDSCH is mapped is smaller than 9 by symbol information of DCI,additional DMRSs mapped to the 11th OFDM symbol may not be transmitted.

In this case, the additional DMRS may be transmitted in maximum two OFDMsymbols, wherein a location of the OFDM symbol to which the additionalDMRS is transmitted may be 6th and 9th OFDM symbols, which are thelocation of the OFDM symbol when the number of additional DMRSs setthrough higher layer signaling is 2.

That is, when three 1-symbol additional DMRSs are set through higherlayer signaling and when symbol information is set to a 7th OFDM symbolor the number of symbols to which the PDSCH is mapped is set to 7through DCI, a location of OFDM symbols to which the additional DMRS ismapped may be the same as a location of an additional DMRS of the caseof being set to two 1-symbol additional DMRSs through higher layersignaling.

In other words, when at least one additional DMRS is mapped to thenumber smaller than the maximum number of symbols to which additionalDMRSs for demodulating downlink data set through higher layer signalingare mapped, the at least one additional DMRS may be mapped to a symbolof the same location as a mapping location of an additional DMRS havingthe smaller number as the maximum number of symbols to which theadditional DMRS is mapped.

Table 22 illustrates an example of a 1-symbol additional DMRS.

TABLE 22 Position of the One 1-symbol Two 1-symbol Three 1-symbol lastPDSCH additional DMRS additional DMRS additional DMRS 13^(th) 11^(th)7^(th), 11^(th) 5^(th), 8^(th), 11^(th) 12^(th) 11^(th) 7^(th), 11^(th)5^(th), 8^(th), 11^(th) 11^(th)  9^(th) 6^(th), 9^(th) 5^(th), 8^(th),11^(th) 10^(th)  9^(th) 6^(th), 9^(th) 6^(th), 9^(th)  9^(th)  9^(th)6^(th), 9^(th) 6^(th), 9^(th)  8^(th)  7^(th) 7^(th) 7^(th)

As illustrated in FIG. 14A, when three 1-symbol additional DMRSs are setthrough higher layer signaling and when a location of a last PDSCH ofsymbol information is set to 12th or when a segment of the PDSCH is setto 13 through DCI, the additional DMRS may be transmitted in 5th, 8th,and 11th OFDM symbols, as illustrated in Tables 19 and 22.

However, as illustrated in FIG. 14B, when three 1-symbol additionalDMRSs are set through higher layer signaling and when a last PDSCHlocation of symbol information is set to 10th, or when a segment of thePDSCH is set to 11 through DCI, an additional DMRS that should be mappedto the 11th OFDM symbol may not be transmitted.

Therefore, in this case, additional DMRSs may be transmitted in 6th and9th OFDM symbols, which are the same locations as locations of symbolsto which the additional DMRSs are mapped in two 1-symbol additionalDMRSs.

Through Embodiment 4, the maximum number of additional DMRSs that may beset semi-statically to the UE through higher layer signaling may be set,and the number of additional DMRSs transmitted to the actual UE may beset through DCI.

That is, the number of additional DMRSs set through higher layersignaling to the UE may be defined to a maximum value of the number ofadditional DMRSs that may be set to the UE. Further, it is possible toset the number and location of additional DMRSs actually transmitted tothe UE through the DCI.

In this case, a specific rule may be set such that the number andlocation of additional DMRSs are directly set to the UE through aspecific DCI field or the number and location of additional DMRSs areset from other information that is flexibly set, such as symbolinformation.

When using this method, there is an effect that can set a DMRS patternthat is most suitable for the symbol information flexibly set to the UE.

For example, because Embodiment 3 is a method of not transmitting arandom DMRS symbol, it may be not regarded that the pattern ofEmbodiment 3 is the DMRS pattern most suitable for symbol information,but in Embodiment 4, because the pattern is set in consideration of thespecific number of additional DMRSs in the symbol information, it may beregarded that the most suitable DMRS pattern is set.

Further, when multiplexing a long PUCCH, a short PUCCH, or an SRS in aslot serving a plurality of UEs having three additional DMRSs in DL,scheduling flexibility can be improved.

Further, flexibility in an MU-MIMO environment can be improved. Forexample, because UEs 1 and 2 may enable MU-paring of corresponding UEsin specific symbol information that is flexibly set even when the numberof additional DMRSs different from each other is set through higherlayer signaling, there is an effect to improve cell throughput.

In this case, the number of additional DMRSs may be reduced according tothe symbol information, but may not be increased, and in order toincrease flexibility of MU-MIMO in specific symbol information, thenumber of additional DMRSs much by one step than the number ofadditional DMRSs set by higher layer signaling may be set through DCIinformation of 1-bit.

In this case, the specific number may be defined to a definite value ormay be defined such that the UE and the base station operate accordingto a specific rule under a specific condition.

In Embodiment 4, a location of a last PDSCH symbol or a PDSCH segment,which is symbol information, may be set from the base station to the UE.In this case, the base station may be defined to notify the UE through apredefined signal (e.g., a physical layer signal or a higher layersignal).

In this case, a location of the last PDSCH symbol or a value of durationof the PDSCH may be notified directly as a definite value by the basestation or may be implicitly notified according to a previously promisedrule between the base station and the UE through another value set tothe UE.

For example, the base station may set an index of a start symbol of thePDSCH and duration of the PDSCH through DCI signaling, and the UE mayimplicitly recognize a location of the last PDSCH symbol based on anindex of a start symbol of the PDSCH and duration of the PDSCH.

The above-described Embodiments 1 to 4 may be implemented independently,but may be implemented in a combination (or merge) form of someembodiments.

Information for indicating whether Embodiments 1 to 4 are applied (orinformation about rules of Embodiments) may be notified to the UEthrough a signal (e.g., a physical layer signal or a higher layersignal) in which the base station predefines to the UE. For example, thebase station may notify the UE of a method to be applied to Embodiments1 to 4 through a predefined signal.

Tables 23 and 15 illustrate an example in which Embodiments 3 and 4among Embodiments 1 to 4 are applied.

TABLE 23 Position of the One 1-symbol Two 1-symbol Three 1-symbol lastPDSCH additional DMRS additional DMRS additional DMRS 13^(th) 11^(th)7^(th), 11^(th) 5^(th), 8^(th), 11^(th) 12^(th) 11^(th) 7^(th), 11^(th)5^(th), 8^(th), 11^(th) 11^(th)  9^(th) 6^(th), 9^(th) 5^(th), 8^(th),11^(th) 10^(th)  9^(th) 6^(th), 9^(th) 6^(th), 9^(th)  9^(th)  9^(th)6^(th), 9^(th) 5^(th), 8^(th)  8^(th)  7^(th) 7^(th) 5^(th), 7^(th) or5^(th)

FIG. 15A illustrates a case in which all of the additional DMRS numbersset through higher layer signaling can be supported.

However, FIGS. 15(a) and 15(b) illustrate an example of a case that maynot support all of the number of additional DMRSs set through higherlayer signaling.

In this case, in FIG. 15B, a method of Embodiment 4 is applied totransmit an additional DMRS in 6th and 9th OFDM symbols according toTable 21, and in FIG. 15C, a method of Embodiment 3 is applied totransmit an additional DMRS in 5th and 8th OFDM symbols according toTable 21.

In a specific example of the proposal, even when only the case for DL orUL is illustrated, the present disclosure may be applicable to all casesof DL/UL, unless it is specified that the technical application islimited to DL or UL.

Further, the proposed method is not limited only to uplink or downlinkcommunication, and the proposed method may be applied to directcommunication between UEs, a base station, a vehicle, a relay node, andthe like.

The Actual Number and Location of Transmitted DMRS for PUSCH withoutHopping

A location of a front-load DMRS for a PUSCH that does not performfrequency hopping is as follows. Further, when the front-load DMRS islocated at a 3rd or 4th symbol of a slot, a location of the additionalDMRS is as follows.

-   -   A first OFDM symbol for scheduled data includes a front-load UL        DMRS.    -   The 3rd or 4th symbol of the slot includes a first symbol of the        front-load DMRS.

The location of the addition DMRS may be the same in UL and DL.

When the first symbol of the front-load DMRS is located at the 3rd or4th symbol of the slot, a DL DMRS location for an UL DMRS for additionalDMRS symbols may be used again for a PUSCH without a hop.

In this case, there is a problem that a location of the additional DMRSis not defined for the case in which the front-load DMRS is located atthe first symbol of the PUSCH.

Therefore, when the front-load DMRS is located at the first symbol ofthe PUSCH, a method of setting a location of the additional DMRS isproposed.

Table 24 illustrates an example of a location of the first symbol of thePUSCH and a location of additional DMRS according to the number ofadditional DMRSs.

TABLE 24 Position of the One Two Three first PUSCH 1-symbol 1-symbol1-symbol symbol(starting additional additional additional from 0^(th))DMRS DMRS DMRS  1^(st) 12^(th) 7^(th), 12^(th) 5^(th), 9^(th), 12^(th) 2^(nd) 12^(th) 7^(th), 12^(th) 5^(th), 9^(th), 12^(th)  3^(rd) 12^(th)8^(th), 12^(th) 6^(th), 9^(th), 12^(th)  4^(th) 12^(th) 8^(th), 12^(th)N/A  5^(th) 12^(th) 9^(th), 12^(th) N/A  6^(th) 12^(th) 9^(th), 12^(th)N/A  7^(th) 12^(th) N/A N/A  8^(th) 12^(th) N/A N/A  9^(th) 12^(th) N/AN/A 10^(th) N/A N/A N/A 11^(th) N/A N/A N/A 12^(th) N/A N/A N/A 13^(th)N/A N/A N/A

In Table 24, a location (hereinafter, referred to as uplink symbolinformation) of a first PUSCH symbol that may be supported according tothe number of additional DMRSs is defined differently. The maximumnumber of additional DMRSs may be set differently in consideration of anRS overhead according to the uplink symbol information.

The number of additional DMRSs for uplink transmission may be set to theUE through higher layer signaling, and uplink symbol information may beflexibly set to the UE.

Therefore, when uplink symbol information that may not support thenumber of additional DMRSs set through higher layer signaling is set, anoperation between the base station and the UE should be defined.

Accordingly, the present disclosure proposes an operation between thebase station and the UE when uplink symbol information that may notsupport the number of additional DMRSs set through higher layersignaling is set.

Embodiment 5

The base station may set a specific value of uplink symbol informationthat may support the number of additional DMRS set semi-statically tothe UE through higher layer signaling to the UE.

For example, in Table 22, in a case of one 1-symbol additional DMRS, oneof values of {1st, 2nd, 3rd, 4th, 5th, 6th, 7th, 8th, and 9th} may beset as a value of uplink symbol information. Further, in the case of one1-symbol additional DMRS, one of values of {1st, 2nd, 3rd, 4th, 5th, and6th} may be set as a value of uplink symbol information.

Using this method, the UE may assume that uplink symbol information thatmay not be supported in the number of additional DMRSs set throughhigher layer signaling is not set from the base station, and may notthus define a separate operation for the case and thus complexity can bereduced.

Alternatively, as in Embodiment 5, an operation between the base stationand the UE may be defined such that uplink symbol information in whichthe number of additional DMRSs set to the UE through higher layersignaling is not defined may be set to the UE.

Embodiment 6

When the number of additional DMRSs set through higher layer signalingmay not be supported, additional DMRSs may be transmitted at locationsof the maximum number of additional DMRSs that may be defined accordingto uplink symbol information.

That is, the method described in Embodiment 4 may also be used fortransmission of DMRSs for uplink data.

Specifically, the number of additional DMRSs set through higher layersignaling transmitted from the base station to the UE may not besupported according to the number of symbols set by uplink symbolinformation.

For example, when the number of additional DMRSs set through higherlayer signaling in Table 24 is 3, additional DMRSs may be mapped andtransmitted to 5th, 9th, and 12th OFDM symbols or 6th, 9th, and 12thOFDM symbols.

However, when a location of a first PUSCH symbol is set to an OFDMsymbol after a 3rd OFDM symbol or when a segment of a symbol to whichthe PUSCH is mapped is smaller than 12 by uplink symbol information ofDCI, the additional DMRS mapped to the 12th OFDM symbol may not betransmitted.

In this case, the additional DMRS may be transmitted in maximum two OFDMsymbols, wherein a location of the OFDM symbol to which the additionalDMRS is transmitted may be 8th and 12th OFDM symbols or 9th and 12thOFDM symbol, which are the location of the OFDM symbol when the numberof additional DMRSs set through higher layer signaling is 2.

That is, when three 1-symbol additional DMRSs are set through higherlayer signaling and when uplink symbol information is OFDM symbols afterthe 3rd OFDM symbol or the number of symbols to which a PDSCH is mappedis set to be smaller than 12 through DCI, a location of the OFDM symbolto which the additional DMRS is mapped may be the same as a location ofthe additional DMRS when setting to two 1-symbol additional DMRSsthrough higher layer signaling.

In other words, when at least one additional DMRS is mapped to thenumber smaller than the maximum number of symbols to which additionalDMRSs for demodulating uplink data set through higher layer signalingare mapped, at least one additional DMRS may be mapped to a symbol ofthe same location as a mapping location of additional DMRS having thesmall number as the maximum number of symbols to which the additionalDMRS is mapped.

Table 25 illustrates an example of a 1-symbol additional DMRS.

TABLE 25 Position of the One Two Three first PUSCH 1-symbol 1-symbol1-symbol symbol(starting additional additional additional from 0^(th))DMRS DMRS DMRS  1^(st) 12^(th) 7^(th), 12^(th) 5^(th), 9^(th), 12^(th) 2^(nd) 12^(th) 7^(th), 12^(th) 5^(th), 9^(th), 12^(th)  3^(rd) 12^(th)8^(th), 12^(th) 6^(th), 9^(th), 12^(th)  4^(th) 12^(th) 8^(th), 12^(th)8^(th), 12^(th)  5^(th) 12^(th) 9^(th), 12^(th) 9^(th), 12^(th)  6^(th)12^(th) 9^(th), 12^(th) 9^(th), 12^(th)  7^(th) 12^(th) 12^(th) 12^(th) 8^(th) 12^(th) 12^(th) 12^(th)  9^(th) 12^(th) 12^(th) 12^(th) 10^(th)N/A N/A N/A 11^(th) N/A N/A N/A 12^(th) N/A N/A N/A 13^(th) N/A N/A N/A

As illustrated in Table 25, a value for an additional DMRS locationcorresponding to N/A in Table 24 may be set to a specific value.

Through Embodiment 6, the maximum number of additional DMRSs that may beset semi-statically to the UE through higher layer signaling may be set,and the number of additional DMRSs transmitted to the actual UE may beset through DCI.

That is, the number of additional DMRSs set through higher layersignaling to the UE may be defined to a maximum value of the number ofadditional DMRSs that may be set to the UE. Further, it is possible toset the number and location of additional DMRSs actually transmitted tothe UE through DCI.

In this case, a specific rule may be set such that the number andlocation of additional DMRSs are directly set to the UE through aspecific DCI field, or the number and location of additional DMRSs areset from other information that is flexibly set such as symbolinformation.

In Embodiment 6, a location of a first PUSCH symbol or a segment of thePUSCH, which is uplink symbol information, may be set from the basestation to the UE. In this case, the base station may be defined tonotify the UE through a predefined signal (e.g., a physical layer signalor a higher layer signal).

In this case, a location of the first PUSCH symbol or a value of thesegment of the PUSCH may be directly notified as a definite value by thebase station or implicitly notified according to a previously promisedrule between the base station and the UE through another value set tothe UE.

The above-described Embodiments 5 and 6 may be implementedindependently, but may be implemented in a combination (or merge) formof some embodiments.

Information (or information on rules of the above embodiments) forindicating whether Embodiments 5 and 6 are applied may be notified tothe UE through a signal (e.g., a physical layer signal or a higher layersignal) predefined by the base station to the UE. For example, the basestation may notify the UE of a method to be applied to Embodiments 5 and6 through a predefined signal.

In a specific example of the proposal, even when only the case for DL orUL is illustrated, the present disclosure may be applicable to all casesof DL/UL, unless it is specified that the technical application islimited to DL or UL.

Further, the proposed method is not limited to uplink or downlinkcommunication, and the proposed method may be applied to directcommunication between UEs, a base station, a vehicle, a relay node, andthe like.

As described above, the front-load DMRS of the PUSCH may be transmittedin the following three locations.

-   -   First OFDM symbol for scheduled data    -   3rd or 4th symbol of the slot

When the front-load DMRS is located at 3rd or 4th, a location of theadditional DMRS may use a location of the existing DL DMRS. However,there is a problem that an additional DMRS location is not defined whenthe front-load DMRS is located at a first OFDM symbol of scheduled data.

Accordingly, the present disclosure proposes a method of setting alocation of an additional DMRS when the front-load DMRS is located atthe first OFDM symbol.

Embodiment 7

FIGS. 16A to 17B are diagrams illustrating another example of a methodof mapping a DMRS proposed in the present disclosure.

Referring to FIGS. 16A to 17B, when an additional DMRS is set to one1-symbol additional DMRS or one 2-symbol additional DMRS (e.g., when afront load DMRS is set to one symbol and an additional DMRS is set toone symbol or when front load DMRSs are continuously set to two symbolsand additional DMRSs are continuously set to two symbols), a location ofthe additional DMRS may be defined so that an extrapolation segment doesnot exceed the maximum ‘x’ number of OFDM symbols (e.g., x is ‘2’).

In this case, as a length of the data transmission segment increases, alocation of the additional DMRS may be set through Equation 7.

y1_new=y1_old+x+1  [Equation 7]

In Equation 7, as a length of the data transmission segment increases,when an additional DMRS may be transmitted to a y1_new location, alocation of the additional DMRS may be changed from y1_old to y1_new.

In Equation 7, y1_new may mean a location of a newly defined additionalDMSR (e.g., OFDM symbol index starting from a front-load DMRS location)as a length of the data transmission segment increases.

y1_old may mean a location of an additional DMRS (e.g., an OFDM symbolindex starting from a front-load DMRS location) before a datatransmission segment length increases.

FIGS. 16A to 16C illustrate an example of locations of additional DMRSsset in one 1-symbol additional DMRS, and FIGS. 17A and 17B illustrate anexample of a location of an additional DMRS set in one 2-symboladditional DMRS.

In case of using Embodiment 7, an extrapolation segment that greatlyaffects estimation performance deterioration of a time-varying channelmay be limited to a predetermined value or less, thereby improving anestimation performance of the time-varying channel.

Further, when the length of the data transmission segment increases, theadditional DMRS location is changed to prevent a plurality of DMRSpatterns from being defined, thereby preventing complexity fromincreasing.

Further, in the case of the PUSCH DMRS, additional DMRS locations can beflexibly set according to a data segment length occupied by the PUSCH.

Embodiment 8

FIGS. 18A to 20B are diagrams illustrating another example of a methodof mapping a DMRS proposed in the present disclosure.

Referring to FIGS. 18A to 20B, when the additional DMRS is set to two1-symbol additional DMRSs or three 1-symbol additional DMRSs (e.g., whena front-load DMRS is set to one symbol and when additional DMRSs are setto two symbols separated from each other, or when a front-load DMRS isset to one symbol and when additional DMRSs are set to three symbolsseparated from each other), a location of the additional DMRS may bedefined so that an extrapolation segment exceeds the maximum ‘x’ numberof OFDM symbols (e.g., x is ‘1’).

In this case, as a length of the data transmission segment increases, alocation of the additional DMRS may be determined according to EquationsY and Z.

When the additional DMRS is set to two 1-symbol additional DMRSs, thelocation of the additional DMRS may be determined by Equation 8.

y1_new=y1_old+x′

y2_new=y2_old+x′+1  [Equation 8]

As a length of the data transmission segment increases, when additionalDMRSs may be transmitted at a y2_new location, two additional DMRSsmapped to symbols separated from each other may be changed andtransmitted according to Equation 8.

FIGS. 18A to 18C illustrate an example in which a location is changedaccording to Equation Y when the additional DMRS is set to two 1-symboladditional DMRSs.

When the additional DMRS is set to three 1-symbol additional DMRS, thelocation of the additional DMRS may be determined by Equation 9.

y1_new=y1_old+x′

y2_new=y2_old+x′+1

y3_new=y3_old+x′+1  [Equation 9]

As a length of the data transmission segment increases, when additionalDMRSs may be transmitted at a y3_new location, two additional DMRSsmapped to symbols separated from each other may be changed andtransmitted according to Equation 9.

FIGS. 19A and 19B illustrate an example in which a location is changedaccording to Equation Z when the additional DMRS is set to two 1-symboladditional DMRSs.

In Equations 8 and 9, y1_new, y2_new, and y3_new may mean newly definedlocations (e.g., OFDM symbol index starting from front-load DMRSlocations) of 1st, 2nd, and 3rd additional DMRSs as a length of the datatransmission segment increases.

1st, 2nd, and 3rd additional DMRSs may mean additional DMRSs in order ofclose to the front-load DMRS, as illustrated in FIGS. 20A to 20B.

In Equations Y and Z, y1_old, y2_old, and y3_old may mean 1st, 2nd, and3rd additional DMRS locations (e.g., OFDM symbol indexes starting fromfront-load DMRS locations) before a length of a data transmissionsegment increases.

Embodiment 8-1

When the number of additional DMRSs is set to k′ or more (e.g., k′=2 ork′=3), a length (x′) of the maximum extrapolation segment may be set tobe smaller than a length x of the maximum extrapolation segment (e.g.,x′<x) when the number of additional DMRSs is set to more than k (e.g.,k=1, in this case, k<k′ is satisfied).

Specifically, when the number of additional DMRSs is set to k′ (k′>k) ormore, an environment may be assumed in which a time-varying channel islarge because a speed of the UE is relatively high, compared with thecase in which the number of additional DMRSs is set to k.

In this case, because the influence of extrapolation causing performancedeterioration may increase due to the time-varying channel, a DMRSpattern may be set to reduce a length of the extrapolation segment.

The methods described in Embodiments 8 and 8-1 correspond to one of theimplementation methods of the present disclosure, and each may beimplemented in an independent manner or in the form of a combination (ormerge) of all or some of the methods.

Information (or information on rules of the embodiments) related towhether the method of Embodiments 8 and 8-1 is applied may be notifiedto the UE through a signal (e.g., physical layer signal or higher layersignal) in which the base station predefines to the UE. For example, thebase station may notify the UE of the method to be applied amongEmbodiments 8 and 8-1 through a predefined signal.

In a specific example of the proposal, even when only the case for DL orUL is illustrated, the present disclosure may be applicable to all casesof DL/UL, unless it is specified that the technical application islimited to DL or UL.

Further, the proposed method is not limited only to uplink or downlinkcommunication, and the proposed method may be applied to directcommunication between UEs, a base station, a vehicle, a relay node, andthe like.

Method for Configuration of the Number of and/or the Location ofAdditional DMRS for Broadcast/Multicast PDSCH and Unicast PDSCH BeforeRRC Configuration

In addition to the PBCH, a front-load DMRS configuration 1 may beapplied to broadcast/multicast.

However, the number and location of additional DMRSs are not defined.Therefore, the following description describes a method of setting thenumber and location of additional DMRS for a PDSCH transmitted before anRRC is configured.

That is, there is a need for a method of setting the number and locationof additional DMRS for a PDSCH (e.g., broadcast/multicast PDSCH, unicastPDSCH before RRC connection) transmitted before the number and locationof additional DMRSs are set to the UE through a predefined signal (e.g.,physical layer signal or higher layer signal) between the base stationand the UE.

Embodiment 9

When a PDSCH is received before higher layer signaling (e.g., RRCsignaling, etc.) is configured, the number of additional DMRSs and alocation of transmitted OFDM symbols may be set according to the numberof preset additional DMRSs and symbol information related to start andend OFDM symbols of the PDSCH set through DCI.

Specifically, in a case of PDSCH transmission (e.g., broadcast/multicastPDSCH, unicast PDSCH before RRC connection) before the number andlocation of additional DMRS is set to the UE through a predefined signal(e.g., physical layer signal or higher layer signal) between the basestation and the UE, the number and location of additional DMRSs may beset to the maximum number and location of values defined for unicastPDSCH transmission in a slot format in which the PDSCH is transmitted.

In this case, the slot format represents an area in which the PDSCH istransmitted and may vary depending on the start and end OFDM symbollocations of the PDSCH. That is, the slot format may mean transmissionduration of the PDSCH according to the start OFDM symbol and the endOFDM symbol of the PDSCH.

Accordingly, the slot format may be referred to as various terms and maybe set to the UE through a DL control channel.

The number and location of additional DMRSs may be defined according toan area in which the unicast PDSCH is transmitted, and the UE mayimplicitly infer the number and location of additional DMRS for thePDSCH transmitted before the number and location of additional DMRSs areset to the UE through a predefined signal (e.g., a physical layer signalor a higher layer signal) between the base station and the UE usinginformation related to an area in which the unicast PDSCH istransmitted.

In this case, the area in which the unicast PDSCH is transmitted may beset to the UE through a last OFDM symbol index of the PDSCH.

Table 26 illustrates an example of the number and location of additionalDMRSs of unicast PDSCH transmission.

TABLE 26 Position Additional DM-RS positions of l last PDSCH mappingtype A PDSCH DL-DMRS-add-pos symbol 0 1 2 3 ≤7 — 8 — 7 9 — 9 6, 9 10 — 96, 9 11 — 9 6, 9 5, 8, 11 12 — 11 7, 11 5, 8, 11 13 — 11 7, 11 5, 8 ,11

In Embodiment 9, the UE may obtain information on a location of the lastPDSCH symbol (hereinafter, referred to as symbol information) throughDCI.

In Embodiment 9, the number and location of additional DMRSs for eachsymbol information may be set as follows, and the UE may implicitlyinfer this through the symbol information.

-   -   When the symbol information is ‘13’, the number of additional        DMRSs is ‘3’, and a location thereof may be located at 5th, 8th,        and 11th OFDM symbols.    -   When the symbol information is ‘10’, the number of additional        DMRSs is ‘2’, and a location thereof may be located at 6th and        9th OFDM symbols.    -   When the symbol information is ‘8’, the number of additional        DMRSs is ‘1’, and a location thereof may be located at the 7th        OFDM symbol.

Using this method, when the last PDSCH symbol is flexibly set, anoptimal additional DMRS may be transmitted in the symbol information andthus it is possible to provide a stable channel estimation performanceeven to a high speed UE.

Embodiment 9-1

In Embodiment 3, the maximum number of additional DMRSs may be limitedto x (e.g., ‘2’).

Specifically, the large number of additional DMRSs (e.g., 2) may be setwhen an accurate channel estimation performance is provided to a UE of ahigh speed to support a high MCS.

However, in the case of a broadcast/multicast PDSCH and a unicast PDSCHbefore RRC connection, a high MCS may not be used, and the large numberof additional DMRSs may cause an unnecessary RS overhead to a UE havingno high speed.

Therefore, in order to stably provide a channel estimation performancewhile appropriately maintaining an RS overhead, the maximum number ofadditional DMRSs may be limited to the specific number or less.

In Embodiment 9-1, the number and location of additional DMRSs for eachsymbol information may be set as follows according to Table 24, and theUE may implicitly infer this through the symbol information.

When the symbol information is ‘13’, the number of additional DMRSs is‘2’, and a location thereof may be located at 7th and 11th OFDM symbols.

When the symbol information is ‘10’, the number of additional DMRS is‘2’, and a location thereof may be located at 6th and 9th OFDM symbols.

When the symbol information is ‘8’, the number of additional DMRS is‘1’, and a location thereof may be located at the 7th OFDM symbol.

Information (or information on rules of the embodiments) related towhether the method of Embodiments 9 and 9-1 is applied may be notifiedto the UE through a signal (e.g., a physical layer signal or a higherlayer signal) predefined by the base station to the UE. For example, thebase station may notify the UE of a method to be applied amongEmbodiments 9 and 9-1 through a predefined signal.

In a specific example of the proposal, even when only the case for DL orUL is illustrated, the present disclosure may be applicable to all casesof DL/UL, unless it is specified that the technical application islimited to DL or UL.

Further, the proposed method is not limited to uplink or downlinkcommunication, and the proposed method may be applied to directcommunication between UEs, a base station, a vehicle, a relay node, andthe like.

FIG. 21 is a flowchart illustrating an example of a method oftransmitting and receiving data of a UE proposed in the presentdisclosure. FIG. 21 is merely for convenience of description and doesnot limit the scope of the present disclosure.

Referring to FIG. 21 , the UE may perform the method(s) described in theabove-described embodiments of the present disclosure. In particular,the UE may support the method described in Embodiments 1 to 9-1. In FIG.21 , a detailed description repeated with the above description will beomitted.

First, the UE may receive downlink control information (DCI) from thebase station (S21010). In this case, the downlink control informationdescribed in Embodiments 1 to 9-1 may include symbol information relatedto a last symbol of the downlink shared channel.

Thereafter, the UE may receive a front-load DMRS (first DMRS) and atleast one additional DMRS (second DMRS) for demodulating downlink data(S21020).

In this case, the number of the at least one second DMRS and a locationof a mapped symbol may be determined according to symbol information, asin the method described in Embodiments 1 to 9-1.

For example, the number of at least one second DMRS and a location ofthe mapped symbol may be set through the method of Embodiment 4.

Alternatively, when downlink data are a broadcast/multicast PDSCHtransmitted before the number and location of at least one additionalDMRS are set or a unicast PDSCH before an RRC connection, the number andlocation of the at least one additional DMRS may be set by Embodiment(s)9 and/or 9-1.

Thereafter, the UE may receive data through the downlink shared channel(S21030).

The UE may be configured with a processor, an RF unit, and a memory, asillustrated in FIGS. 23 to 26 , and the processor may control the RFunit to receive downlink control information (DCI) from the basestation.

In this case, the downlink control information described in Embodiments1 to 9-1 may include symbol information related to a last symbol of thedownlink shared channel.

Further, the processor may control the RF unit to receive a first DMSRand at least one second DMRS for demodulating downlink data.

In this case, the number of the at least one second DMRS and a locationof the mapped symbol may be determined according to symbol information,as in the method described in Embodiments 1 to 9-1.

For example, the number of at least one second DMRS and a location ofthe mapped symbol may be set through the method of Embodiment 4.

Alternatively, when the downlink data are a broadcast/multicast PDSCHtransmitted before the number and location of the at least oneadditional DMRS are set or a unicast PDSCH before the RRC connection,the number and location of the at least one additional DMRS may be setby Embodiment(s) 9 and/or 9-1.

Further, the processor may control the RF unit to receive downlink datafrom the base station.

FIG. 22 is a flowchart illustrating an example of a method oftransmitting and receiving data of a base station proposed in thepresent disclosure. FIG. 22 is merely for convenience of description anddoes not limit the scope of the present disclosure.

Referring to FIG. 22 , the base station may perform the method(s)described in the above-described embodiments of the present disclosure.The base station may support the method described in Embodiments 1 to9-1. In FIG. 22 , a detailed description repeated with the abovedescription will be omitted.

First, the base station may transmit downlink control information (DCI)to the UE (S22010). In this case, the downlink control informationdescribed in Embodiments 1 to 9-1 may include symbol information relatedto a last symbol of the downlink shared channel.

Thereafter, the base station may transmit a front-load DMRS (first DMRS)and at least one additional DMRS (second DMRS) for demodulating downlinkdata (S22020).

In this case, the number of the at least one second DMRS and a locationof the mapped symbol may be determined according to symbol information,as in the method described in Embodiments 1 to 9-1.

For example, the number of at least one second DMRS and a location ofthe mapped symbol may be set through the method of Embodiment 4.

Alternatively, when the downlink data are a broadcast/multicast PDSCHtransmitted before the number and location of at least one additionalDMRS are set or a unicast PDSCH before the RRC connection, the numberand location of the at least one additional DMRS may be set byEmbodiment(s) 9 and/or 9-1.

Thereafter, the base station may transmit data through the downlinkshared channel (S22030).

The base station may be configured with a processor, an RF unit, and amemory, as illustrated in FIGS. 23 to 26 , and the processor may controlthe RF unit to transmit downlink control information (DCI) from the UE.

In this case, the downlink control information described in Embodiments1 to 9-1 may include symbol information related to a last symbol of thedownlink shared channel.

Further, the processor may control the RF unit to transmit a first DMRSand at least one second DMRS for demodulating downlink data.

In this case, the number of the at least one second DMRS and a locationof the mapped symbol may be determined according to symbol information,as in the method described in Embodiments 1 to 9-1.

For example, the number of at least one second DMRS and a location ofthe mapped symbol may be set through the method of Embodiment 4.

Alternatively, when downlink data are a broadcast/multicast PDSCHtransmitted before the number and location of at least one additionalDMRS are set or a unicast PDSCH before the RRC connection, the numberand location of the at least one additional DMRS may be set byEmbodiment(s) 9 and/or 9-1.

Further, the processor may control the RF unit to transmit downlink datato the UE.

General Apparatus in which the Present Disclosure May be Applied

FIG. 23 is a block diagram illustrating a configuration of a wirelesscommunication device to which methods suggested in the presentdisclosure may be applied.

Referring to FIG. 23 , a wireless communication system includes an eNB2310 and a plurality of UEs 2320 located within an eNB 2310 area.

The eNB and the UE may each be represented with a wireless device.

The eNB 2310 includes a processor 2311, a memory 2312, and a radiofrequency module (RF module) 2313. The processor 2311 implements afunction, a process, and/or a method suggested in FIGS. 1 to 23 . Layersof a wireless interface protocol may be implemented by the processor.The memory 2312 is connected to the processor to store variousinformation for driving the processor. The RF module 2313 is connectedto the processor to transmit and/or receive an RF signal.

The UE 2320 includes a processor 2321, a memory 2322, and an RF module2323.

The processor 2321 implements a function, a process, and/or a methodsuggested in FIGS. 1 to 22 . Layers of a wireless interface protocol maybe implemented by the processor. The memory 2322 is connected to theprocessor to store various information for driving the processor. The RFmodule 1923 is connected to the processor to transmit and/or receive anRF signal.

The memories 2312 and 2322 may exist at the inside or the outside of theprocessors 2311 and 2321 and may be connected to the processors 2311 and2321, respectively, by well-known various means.

Further, the eNB 2310 and/or the UE 2320 may have a single antenna or amultiple antenna.

FIG. 24 is a block diagram illustrating a configuration of acommunication device according to an embodiment of the presentdisclosure.

In particular, FIG. 24 is a diagram illustrating in more detail the UEof FIG. 23 .

Referring to FIG. 24 , the UE may include a processor (or digital signalprocessor (DSP)) 2410, an RF module (or RF unit) 2435, a powermanagement module 2405, an antenna 2440, a battery 2455, a display 2415,a keypad 2420, a memory 2430, a subscriber identification module (SIM)card 2425 (this element is an option), a speaker 2445, and a microphone2450. The UE may include a single antenna or multiple antennas.

The processor 2410 implements a function, a process, and/or a methodsuggested in FIGS. 11A to 22 . Layers of a wireless interface protocolmay be implemented by the processor.

The memory 2430 is connected to the processor and stores informationrelated to an operation of the processor. The memory 2430 may exist atthe inside or the outside of the processor and may be connected to theprocessor by well-known various means.

The user inputs, for example, command information such as a phone numberby pressing (touching) a button of the keypad 2420 or by voiceactivation using the microphone 2450. The processor processes to performan appropriate function such as reception of such command informationand calling with a phone number. Operational data may be extracted fromthe SIM card 2425 or the memory 2430. Further, for user recognition andconvenience, the processor may display command information or drivinginformation on the display 2415.

The RF module 2435 is connected to the processor to transmit and/orreceive an RF signal. In order to start communication, for example, inorder to transmit a wireless signal constituting voice communicationdata, the processor transfers command information to the RF module. Inorder to receive and transmit a wireless signal, the RF module isconfigured with a receiver and a transmitter. The antenna 2440 performsa function of transmitting and receiving a wireless signal. Whenreceiving a wireless signal, the RF module may transfer a signal inorder to process by the processor and convert a signal with a base band.The processed signal may be converted to audible or readable informationoutput through the speaker 2445.

FIG. 25 is a diagram illustrating an example of an RF module of awireless communication device to which a method proposed in thisdisclosure may be applied.

Specifically, FIG. 25 illustrates an example of an RF module that may beimplemented in a frequency division duplex (FDD) system.

First, in a transmission path, the processor described in FIGS. 24 and25 processes data to be transmitted and provides an analog output signalto a transmitter 2510.

Within the transmitter 2510, the analog output signal is filtered by alow pass filter (LPF) 2511 so as to remove images caused bydigital-to-analog conversion (ADC), is up-converted from a baseband toan RF by a mixer 2512, and is amplified by a Variable Gain Amplifier(VGA) 2513, and the amplified signal is filtered by a filter 2514, isadditionally amplified by a power amplifier (PA) 2515, is routed throughduplexer(s) 2550/antenna switch(s) 2560, and is transmitted through anantenna 2570.

Further, in a receiving path, the antenna 2570 receives signals from theoutside and provides the received signals, and the signals are routedthrough the antenna switch(s) 2560/duplexers 2550 and are provided to areceiver 2520.

Within the receiver 2520, the received signals are amplified by a LowNoise Amplifier (LNA) 2523, are filtered by a bandpass filter 2524, andare down-converted from an RF to a baseband by a mixer 2525.

The down-converted signal is filtered by a low pass filter (LPF) 2526and is amplified by a VGA 2527 to obtain an analog input signal, whichis provided to the processor described in FIGS. 12 and 13 .

Further, a local oscillator (LO) generator 2540 generates transmittingand receiving LO signals and provides the transmitting and receiving LOsignals to the mixer 2512 and the mixer 2525, respectively.

Further, in order to generate transmitting and receiving LO signals atappropriate frequencies, a Phase Locked Loop (PLL) 2530 receives controlinformation from the processor and provides control signals to the LOgenerator 2540.

Further, the circuits illustrated in FIG. 25 may be arranged differentlyfrom the configuration illustrated in FIG. 25 .

FIG. 26 is a diagram illustrating another example of an RF module of awireless communication device to which a method proposed in thisdisclosure may be applied.

Specifically, FIG. 26 illustrates an example of an RF module that may beimplemented in a time division duplex (TDD) system.

A transmitter 2610 and receiver 2620 of the RF module in the TDD systemhave the same structure as that of a transmitter and receiver of an RFmodule in an FDD system.

Hereinafter, the RF module of the TDD system will be described only fora structure that differs from the RF module of the FDD system, and adescription of the same structure will be described with reference toFIG. 25 .

A signal amplified by a power amplifier (PA) 2615 of the transmitter isrouted through a band select switch 2650, a band pass filter (BPF) 2660,and an antenna switch(s) 2670 and is transmitted through an antenna2680.

Further, in a receiving path, the antenna 2680 receives signals from theoutside and provides the received signals, and the signals are routedthrough the antenna switch(s) 2670, the BPF 2660, and the band selectswitch 2650 and are provided to the receiver 2620.

In the foregoing embodiments, the elements and characteristics of thepresent disclosure have been combined in specific forms. Each of theelements or characteristics should be considered to be optional unlessotherwise described explicitly. Each of the elements or characteristicsmay be implemented in a form that does not combine with other elementsor characteristics. Further, some of the elements and/or thecharacteristics may be combined to constitute an embodiment of thepresent disclosure. The order of the operations described in theembodiments of the present disclosure may be changed. Some of theelements or characteristics of an embodiment may be included in anotherembodiment or may be replaced with corresponding elements orcharacteristics of another embodiment. It is evident that an embodimentmay be configured by combining claims having no explicit citationrelation in the claims or may be included as a new claim by amendmentsafter filing an application.

The embodiment according to the present disclosure may be implemented byvarious means, for example, hardware, firmware, software, or acombination thereof. In the case of an implementation by hardware, theembodiment of the present disclosure may be implemented by one or moreapplication specific integrated circuits (ASICs), digital signalprocessors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), field programmable gate arrays(FPGAs), processors, controllers, microcontrollers, and microprocessors.

In the case of an implementation by firmware or software, the embodimentof the present disclosure may be implemented in the form of a module,procedure or function for performing the aforementioned functions oroperations. A software code may be stored in the memory to be driven bythe processor. The memory may be located inside or outside the processorto exchange data with the processor by various known means.

It is evident to those skilled in the art that the present disclosuremay be materialized in other specific forms without departing fromessential characteristics thereof. Accordingly, the detailed descriptionshould not be construed as being limitative from all aspects, but shouldbe construed as being illustrative. The scope of the present disclosureshould be determined by reasonable analysis of the attached claims, andall changes within the equivalent range of the present disclosure areincluded in the scope of the present disclosure.

Further, for convenience of description, embodiments are described withreference to each drawing, but embodiments described with reference toeach drawing may be combined to implement a new embodiment. According tothe needs of those skilled in the art, it is also within the scope ofthe present disclosure to design a computer-readable recording mediumhaving a program recorded thereon for executing the above-describedembodiments.

A method of transmitting and receiving a reference signal according tothis disclosure is not limited to a configuration and method of theembodiments, and for various changes of the embodiments, the entire or aportion of embodiments may be selectively combined.

A method of transmitting and receiving a reference signal of the presentdisclosure may be implemented into a processor readable code in aprocessor readable recording medium provided in a network device. Theprocessor readable recording medium includes an entire kind of recorddevice that stores data that may be read by a processor. The processorreadable recording medium may include, for example, a read-only memory(ROM), a random-access memory (RAM), a CD-ROM, a magnetic tape, a floppydisk, and an optical data storage apparatus and includes implementationin a form of a carrier wave such as transmission through Internet.Further, in the processor readable recording medium, codes that aredistributed in a computer system connected to a network and in which aprocessor may read with a distributed method may be stored and executed.

Further, in the foregoing description, embodiments of the presentdisclosure are described, but the present disclosure is not limited tothe foregoing specific embodiment and changes and variations may be madeby those having ordinary skill in the art without departing from thespirit or scope of the following claims and all such changes,modifications and alterations should not be individually understood fromthe scope of the present disclosure.

Further, in this disclosure, both the object disclosure and the methoddisclosure are described, and a description of both disclosures may besupplementally applied, as needed.

In a wireless communication system of the present disclosure, an RRCconnection method has been described in an example applied to a 3GPPLTE/LTE-A system, but may be applied to various wireless communicationsystems in addition to a 3GPP LTE/LTE-A system.

1. A method performed by a terminal operating in a wirelesscommunication system, the method comprising: receiving, from a basestation, configuration information related to a number of symbolpositions for receiving additional demodulation reference signal (DMRS)on a physical downlink shared channel (PDSCH); receiving, from the basestation, Downlink Control Information (DCI) for scheduling the PDSCH;determining, by the terminal, at least one symbol position for receivingthe additional DMRS on the PDSCH, based on (i) the configurationinformation and (ii) a duration between (a) a first symbol of a slotrelated to the PDSCH and (b) a last symbol of the PDSCH in the slotrelated to the PDSCH; and receiving, from the base station, theadditional DMRS on the at least one symbol position on the PDSCH,wherein determining the at least one symbol position for receiving theadditional DMRS on the PDSCH based on (i) the configuration informationand (ii) the duration between (a) the first symbol of the slot relatedto the PDSCH and (b) the last symbol of the PDSCH in the slot related tothe PDSCH comprises: based on the configuration information includinginformation for 3 symbol positions for the additional DMRS, and based onthe duration between (a) the first symbol of the slot related to thePDSCH and (b) the last symbol of the PDSCH in the slot related to thePDSCH being one of 12 in symbols, 13 in symbols, or 14 in symbols:determining the at least one symbol position for the additional DMRS asequal to a symbol whose symbol index is 5, a symbol whose symbol indexis 8, and a symbol whose symbol index is 11, in the slot; based on theconfiguration information including information for 3 symbol positionsfor the additional DMRS, and based on the duration between (a) the firstsymbol of the slot related to the PDSCH and (b) the last symbol of thePDSCH in the slot related to the PDSCH being one of 11 in symbols or 10in symbols: determining the at least one symbol position for theadditional DMRS as equal to a symbol whose symbol index is 6 and asymbol whose symbol index is 9, in the slot; and based on theconfiguration information including information for 3 symbol positionsfor the additional DMRS, and based on the duration between (a) the firstsymbol of the slot related to the PDSCH and (b) the last symbol of thePDSCH in the slot related to the PDSCH being 9 in symbols: determiningthe at least one symbol position for the additional DMRS as equal to asymbol whose symbol index is 7, in the slot.
 2. The method of claim 1,further comprising: receiving, from the base station, the PDSCH based onthe additional DMRS.
 3. The method of claim 1, wherein a 6th symbol inthe slot related to the PDSCH is the symbol whose symbol index is 5,wherein a 7th symbol in the slot related to the PDSCH is the symbolwhose symbol index is 6, wherein a 8th symbol in the slot related to thePDSCH is the symbol whose index is 7, wherein a 9th symbol in the slotrelated to the PDSCH is the symbol whose symbol index is 8, wherein a10th symbol in the slot related to the PDSCH is the symbol whose symbolindex is 9, and wherein a 12th symbol in the slot related to the PDSCHis the symbol whose symbol index is
 11. 4. The method of claim 1,wherein the configuration information is received from the base stationthrough Radio Resource Control (RRC) signaling.
 5. The method of claim1, wherein the configuration information is further related to a maximumnumber of symbols for (i) a front-loaded DMRS on the PDSCH and (ii) theadditional DMRS.
 6. The method of claim 5, further comprising:receiving, from the base station, the front-loaded DMRS on at least onesymbol position for the front-loaded DMRS on the PDSCH, based on theconfiguration information.
 7. A terminal configured to operate in awireless communication system, the terminal comprising: a transceiver;at least one processor; and at least one computer memory operablyconnectable to the at least one processor and storing instructions that,when executed by the at least one processor, perform operationscomprising; receiving, from a base station, configuration informationrelated to a number of symbol positions for receiving additionaldemodulation reference signal (DMRS) on a physical downlink sharedchannel (PDSCH); receiving, from the base station, Downlink ControlInformation (DCI) for scheduling the PDSCH; determining, by theterminal, at least one symbol position for receiving the additional DMRSon the PDSCH, based on (i) the configuration information and (ii) aduration between (a) a first symbol of a slot related to the PDSCH and(b) a last symbol of the PDSCH in the slot related to the PDSCH; andreceiving, from the base station, the additional DMRS on the at leastone symbol position on the PDSCH, wherein determining the at least onesymbol position for receiving the additional DMRS on the PDSCH based on(i) the configuration information and (ii) the duration between (a) thefirst symbol of the slot related to the PDSCH and (b) the last symbol ofthe PDSCH in the slot related to the PDSCH comprises: based on theconfiguration information including information for 3 symbol positionsfor the additional DMRS, and based on the duration between (a) the firstsymbol of the slot related to the PDSCH and (b) the last symbol of thePDSCH in the slot related to the PDSCH being one of 12 in symbols, 13 insymbols, or 14 in symbols: determining the at least one symbol positionfor the additional DMRS as equal to a symbol whose symbol index is 5, asymbol whose symbol index is 8, and a symbol whose symbol index is 11,in the slot; based on the configuration information includinginformation for 3 symbol positions for the additional DMRS, and based onthe duration between (a) the first symbol of the slot related to thePDSCH and (b) the last symbol of the PDSCH in the slot related to thePDSCH being one of 11 in symbols or 10 in symbols: determining the atleast one symbol position for the additional DMRS as equal to a symbolwhose symbol index is 6 and a symbol whose symbol index is 9, in theslot; and based on the configuration information including informationfor 3 symbol positions for the additional DMRS, and based on theduration between (a) the first symbol of the slot related to the PDSCHand (b) the last symbol of the PDSCH in the slot related to the PDSCHbeing 9 in symbols: determining the at least one symbol position for theadditional DMRS as equal to a symbol whose symbol index is 7, in theslot.
 8. The terminal of claim 7, wherein the last symbol of the PDSCHin the slot related to the PDSCH is based on the DCI.
 9. The terminal ofclaim 7, wherein a 6th symbol in the slot related to the PDSCH is thesymbol whose symbol index is 5, wherein a 7th symbol in the slot relatedto the PDSCH is the symbol whose symbol index is 6, wherein a 8th symbolin the slot related to the PDSCH is the symbol whose index is 7, whereina 9th symbol in the slot related to the PDSCH is the symbol whose symbolindex is 8, wherein a 10th symbol in the slot related to the PDSCH isthe symbol whose symbol index is 9, and wherein a 12th symbol in theslot related to the PDSCH is the symbol whose symbol index is
 11. 10.The terminal of claim 7, wherein the configuration information isreceived from the base station through Radio Resource Control (RRC)signaling.
 11. The terminal of claim 7, wherein the configurationinformation is further related to a maximum number of symbols for (i) afront-loaded DMRS on the PDSCH and (ii) the additional DMRS.
 12. Theterminal of claim 11, wherein the operations further comprise:receiving, from the base station through the transceiver, thefront-loaded DMRS on at least one symbol position for the front-loadedDMRS on the PDSCH, based on the configuration information.
 13. A methodperformed by a base station operating in a wireless communicationsystem, the method comprising: transmitting, to a terminal,configuration information related to a number of symbol positions forreceiving additional demodulation reference signal (DMRS) on a physicaldownlink shared channel (PDSCH); transmitting, to the terminal, DownlinkControl Information (DCI) for scheduling the PDSCH; mapping, by the basestation, an additional DMRS to at least one symbol position forreceiving the additional DMRS on the PDSCH, wherein the at least onesymbol position to which the additional DMRS is mapped is determinedbased on (i) the configuration information and (ii) a duration between(a) a first symbol of a slot related to the PDSCH and (b) a last symbolof the PDSCH in the slot related to the PDSCH; and transmitting, to theterminal, the additional DMRS on the at least one symbol position on thePDSCH, wherein the at least one symbol position to which the additionalDMRS is mapped is determined according to: based on the configurationinformation including information for 3 symbol positions for theadditional DMRS, and based on the duration between (a) the first symbolof the slot related to the PDSCH and (b) the last symbol of the PDSCH inthe slot related to the PDSCH being one of 12 in symbols, 13 in symbols,or 14 in symbols: the at least one symbol position for the additionalDMRS is equal to a symbol whose symbol index is 5, a symbol whose symbolindex is 8, and a symbol whose symbol index is 11, in the slot; based onthe configuration information including information for 3 symbolpositions for the additional DMRS, and based on the duration between (a)the first symbol of the slot related to the PDSCH and (b) the lastsymbol of the PDSCH in the slot related to the PDSCH being one of 11 insymbols or 10 in symbols: the at least one symbol position for theadditional DMRS is equal to a symbol whose symbol index is 6 and asymbol whose symbol index is 9, in the slot; and based on theconfiguration information including information for 3 symbol positionsfor the additional DMRS, and based on the duration between (a) the firstsymbol of the slot related to the PDSCH and (b) the last symbol of thePDSCH in the slot related to the PDSCH being 9 in symbols: the at leastone symbol position for the additional DMRS is equal to a symbol whosesymbol index is 7, in the slot.
 14. The method of claim 13, wherein thelast symbol of the PDSCH in the slot related to the PDSCH is based onthe DCI.
 15. The method of claim 13, wherein a 6th symbol in the slotrelated to the PDSCH is the symbol whose symbol index is 5, wherein a7th symbol in the slot related to the PDSCH is the symbol whose symbolindex is 6, wherein a 8th symbol in the slot related to the PDSCH is thesymbol whose index is 7, wherein a 9th symbol in the slot related to thePDSCH is the symbol whose symbol index is 8, wherein a 10th symbol inthe slot related to the PDSCH is the symbol whose symbol index is 9, andwherein a 12th symbol in the slot related to the PDSCH is the symbolwhose symbol index is
 11. 16. The method of claim 13, wherein theconfiguration information is received from the base station throughRadio Resource Control (RRC) signaling.
 17. The method of claim 13,wherein the configuration information is further related to a maximumnumber of symbols for (i) a front-loaded DMRS on the PDSCH and (ii) theadditional DMRS.
 18. The method of claim 17, further comprising:transmitting, to the terminal, the front-loaded DMRS on at least onesymbol position for the front-loaded DMRS on the PDSCH, based on theconfiguration information.